Errors which can occur with Mods

Problems with mods usually occur right at the beginning, if they either were installed incorrectly (see above), or if Anno got a recent patch update. If you encounter problems, it is best to contact the creator of the mod directly. Contact details can be found from where you downloaded the mod. Sometimes they have also pot their prefered ways of contact in a readme.txt or similar in the mod files.

If you encounter problems and don't know where they may have originated, here's a bit of general troubleshooting:
Try different saves. Even a savegame can break sometimes.
If the mod collection is new, see if mods are incompatable with each other. Some mods also need other mods as a base to function properly (usually found on the download page).
Deactivate all mods (just rename the folder "mods") and see if the problem persists. was there an update, and/or test if it also exists if you create a new game to see if it comes from Anno/Uplay itself. (Remember: Modded savegames = no support)
If the Mod Loader doesn't want to run at all, it can help to reinstall Visual C++ (make sure you have the right version), but this is rather unlikely, and Anno usually has a problem too if that is the case. You can find the download here.
More likely causes are other programms like Steam (where you have switch to offline mode) or Epic Game Launcher. In the latter case you have to uninstall the Epic client, and then install/start Anno "normally" via Uplay (no guarantee but it works most of the time).

For general knowledge, the need to exchange information, etc. some modders also have a discord server, which you can join: https://discord.gg/4XQTznE