This happens when there is some mod that is not compatible with the latest game updates. It does not matter if you think all mods are "up to date". You will have to remove the mods and add them back a few at a time to see which one is causing the issue. One way to shorten this process is to uncheck the script mod option or remove all script mods.
These are the mods that most often cause the issue. If the game loads with script mods disabled, then you have a place to start. Instead of having to remove all the mods to test, remove all script mods (an exception can be made for some, such as MC Commander, as we know that one is up to date. After removing add them back one by one to see which is causing the issue.