Originally Posted by Raze

No, you don't need a crafting station, or the recipe. In the inventory you can right click one of the items and 'combine with', then add the other.

If you email supportdos2@larian.com with your save (or email/PM a Dropbox or Google drive link, etc), I can take a look at it. If it isn't an issue with a mod, maybe the combination doesn't work with a particulr type of potion bottle, or something. Also include the full list of non-Larian mods enabled and/or the modsettings.lsx file from your profile folder.
Each save is a folder in the '..\Documents\Larian Studios\Divinity Original Sin 2 Definitive Edition\PlayerProfiles\<ProfileName>\Savegames\Story' folder.
In Windows Explorer you can zip a file or folder by right clicking on it/them and selecting 'Send To | Compressed (zipped) Folder' (and similarly in OSX/Finder).

Thank you very much mate I will do that for sure!