I used to have Fallout New Vegas from Steam, and all the mods from Vortex worked fine on there. But I read that GOG's version of New Vegas has less bugs than Steam's version, so I downloaded New Vegas from GOG and then I uninstalled New Vegas from my Steam library (and my PC). I started a new game, but the mods from Vortex didn't deploy. I've tried selecting the update/repair option several times for GOG's New Vegas, restarting the computer, but nothing has worked. Vortex and GOG are all up to date.
Any help in getting my Vortex mods to work in GOG's New Vegas would be greatly appreciated, thanks.

Have you tried looking for a solution in the Fallout specific subforum?:
https://www.gog.com/forum/fallout_series

This one's for Fallout 3 + Vortex, but since it's the same engine it might work for New Vegas as well:
https://www.gog.com/forum/fallout_series/trouble_modding_gog_fallout_3_windows_10_nexusmods_vortex/post5

"The problem was due to the initial setup of the game.

In the launcher you have a link to the DATA FILES. They were not checked and the Mods required all the DLCs.

Once I checked the DLCs to activate them the Mods started working and installed correctly."

Never used vortex, used the previous incarnation and it was basic and not great. Use a proper mod manager and ditch vortex. I have used a few mod managers for fallout games and elder scrolls games (offline installers of course, no galaxy) and they work great and once you understand a few concepts are quite powerful.

I played it 140h and finished it last week and never had any problem with mod organizer. It's not hard to understand it and if you make mistakes, it's easy to reverse it has it do not modify your game data folder.

Vortex is a fairly terrible piece of software. Try a different mod manager.

What do you recommend, and where can I find it? What do you consider a proper mod manager, and where can I get one? I'll check them out, thanks I went into data files, and everything except one thing was checked. I checked it and also checked add loose files. I started the game, but no change. All the DLCs were active since the very beginning anyways, when I first downloaded and played it from GOG.
Thanks though.

Mod organiser:
https://www.nexusmods.com/skyrimspecialedition/mods/6194

That is the tool I always use. Oh, and you might want to check out take of two wastelands.

Mod organizer 2 is the best for any bethesda game, after a few minutes to understand how to use it, it will be really simple to mod your games. As i said before i played 140h and never had any problem with mods same with fallout 3 with 130h.

I can't complete the tutorial. I tried to download a mod for FNV from the nexus, and nothing happens. It doesn't appear in the download list or anything.
This is endlessly aggravating. I wasted redownloading the game from GOG. I even had it download to the games folder outside of program files like people recommend on Reddit.
I'm just going back to Steam's version.
Thanks anyways everyone.

The steam and gog copies are identical other than the CEG drm in the steam one is active. Modding is not a simple thing, there are readers with most mods, install instructions. You will need to understand these things before things work, and even then it might not work. This is because it is individuals giving their own free time to provide extra content or function to a product which is not built for it. Big companies have teams of testers and access to the source code to do things properly. Therefore if that’s too much effect, maybe just forget about mods as you will just get frustrated. Me, I have a decent mod list of around 30 mods for each fallout 3 and NV all of which run pretty well. I can dig out this list when I am back in 3 weeks. Or you can look at mod lists on nexus, they step through these things.
Some tips though for any modding:
Never install anything to program files or x86.
Don’t use galaxy.
Download all necessary files fully (ensure they complete correctly.
Read the readmes included with most mods or install instructions.
Note the requirements for the mod, for instance some need the script extended to work.

You have to link your nexus account on mod organizer first, and select download with manager or manual and add it to mod organizer if you prefer this method. If the tutorial is hard to understand, check a video on internet or check this if you prefer reading https://wiki.step-project.com/Guide:Mod_Organizer

Feels bad, I’m having the exact same version. Going back to steam version as well, at least GOG version was pretty cheap but not worth in the end.

I have F:NV and all the GOG version of Bethesda games, Vortex works with them all. I just clean uninstalled F:NV removed all regedits and %appdata% and updated to a new Vortex then reinstalled F:NV via Galaxy. Vortex saw and recognized the GOG install and even shows them as the game store. I just installed mods without issue, activated and worked fine. (see attached pictures)

It sounds like you have old files from the steam install and steam config artifacts in vortex messing up your GOG version. From a clean install of F:NV it works without issue. As a note you will need to launch it first and set your data files and options before loading Vortex so the right flies in %appdata% are generated. You may need to delete all the old F:NV files from steam too and remove it from Vortex and install it fresh.

TL;DR Fallout: New Vegas GOG edition works fantastic with Vortex no issues getting Vortex to see it or install mods.

Not fully, since many of the mods themselves that are on Nexus do not work with the GOG version of Bethesda games, at least not for Skyrim.

I'm not sure if other GOG versions of Bethesda games have the same problem too, but Skyrim definitely does.

Well that's completely false, (see attached image)

I have 63 mods actively working in Skyrim with no issues: Ordinator, Apocalypse, QWM, SkyUI, USSEP, Inigo, EBT, Immersive citizens, Immersive Creatures, Immersive weapons, immersive armors, RDO, CRF, Diverse Dragons, total character makeover, Ai overhaul, forgotten dungeons, midden expanded, JK Skyrim, Skyrim 2020, SMIM, immersive creatures, Skyrim Sewers, immersive dungeons, dungeons revisited, blended roads, Parthunax, notice board, brotherhood of old, immersive world encounters, Moonpath, Project AHO, Undeath - and remastered, No BS projectile, Nature of Wild lands, Folkvanger, Majestic Mountains, Perks for NPC's, custom randomized loot mod. and a hand full of others that I'm to lazy to type in.

All in all 35GB of mod goodness all working without issue on the GOG version.