I realized after I posted that I worded the topic title wrong. I've successfully modded Oblivion with nexus mods, so it's not a problem with their mods. This is more specifically to do with modmanagers not working.

Google "dazip is already installed" and you should easily find the nexus forum thread from 2015 that explains the exact problem I'm having (and was never solved). I'm using Windows 8.1, have DAO installed on an SSD (not the primary OS drive), and none of the three mod managers (DAO modmanager, DAmodder and DAupdater) will install any mods. My preference is DAO modmanager, but every time I try to install a mod it gives me that message and does nothing. I've tried every suggestion I could find through forum and google searches, but nothing has made a difference.

Anyone here have a clue how to fix this?

Probably this isn't much help. I have the game installed to C:\GOG Games\Dragon Age Origins and DAO-Modmanager works fine. Maybe reinstall to another location?

I just remembered to update this thread. The problem was the Windows registry string path being changed from "Path" to "Path_", which (from what I've seen said about it) was done to prevent players with the Origin client installed from having the client replace the GOG version with the Origin version. I ran the included "regkey-switch" command script, which added the proper path, and all three mod managers are working fine now.

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Hi Snow-Mad,

Did you resolve this?
I have uninstalled both my Origins and my Steam DAO due to the loss of DLC after using Vortex to install mods.
I have purchased GoG's DAO and also downloaded the DAO ModManager from Nexus....
but, much as you describe, I cannot seem to get the DAO ModManager to work....
but also, I do not see an override folder to put my mods into (as a workaround for those mods I cannot install via the DAO ModManager).
I am on Windows 10. You did not mention which sys you are working with?
And I have a new gaming computer so....
after reading all the threads in GoG's forums and on Nexus....
I seem to be out of options.
Please let me know if you are still having trouble...
or if you found another way... I would sincerely appreciate it.
And who knows? maybe I can help you some way!
Best to you!

I suggest you plow through the nexus comment section of the mod. I'm sure your solution will be there somewhere. As for the override folder, you can create that yourself.

I know its been a while but if you get this could you please give a guide on how to do this? i am not tech savvy