You mean Might & Magic X, right? Bad news: it's a very common bug and it never got patched (thanks, Ubisoft). Good news: we know how to fix it.
There are three solutions:
1. You have to be online
(Uplay must be connected to Internet, no offline mode
). It's a leftover from the Early Access version of the game - Uplay has to check if you're running the full version (8 GB) instead of EA version (4 GB). Check the game size too, just to be sure. This one worked for me back when I was playing the game for the first time.
2. You can't have a horse/mule hireling in your party
. Lev should let you know about it through his dialogue (saying something like "whoa, we can't fly to the Forge with a horse"), but the game may bug out and not display this line. Check if you have a horse in your hireling slot and if you do - dismiss it (click on it and choose the right dialogue line). You can re-hire it in Sorpigal once you're done with the Elemental Forge quest.
3. If nothing else works, you can edit one of the game files to bypass the online check. Don't forget to make a backup copy of the file and your save files before editing!
The game does not support Steam/Uplay cloud sync and will not make an auto-backup of your save.
Find the game folder - if you bought a physical copy (box/disk) or digital through Uplay, it should be in Program Files\Ubisoft Game Launcher\games\Might & Magic(R) X Legacy. If you have the Steam version, then look for Program Files\Steam\steamapps\common\Might & Magic X - Legacy.
Find a file called LevDialog.xml - you should find it in Might and Magic X Legacy_Data\StreamingAssets\Dialog. Make a backup copy of the file.
You can copy-paste it on your Desktop, just so you have an unedited copy in case something goes wrong.
Open the file (if you don't have the software for that, you can download and install Notepad++, it's freeware) and find all the lines that look like this:
condition xsi:type="PrivilegeUnlockedCondition" privilegeID="1001" failState="DISABLED"
There should be four of them total. Add <!-- and --> at the beginning and at the end of these lines or
delete them entirely. Save the file and run the game. Now you should be able to fly to the Forge without any other problems.
Good luck with the rest of the game!