Hi just had this problem myself!!
1) uninstall Smapi and reinstall the newest version (3.13.2)
2) uninstall Stardew and reinstall it (Steam version will keep your save data on Steam and when you reinstall, it'll be there again. Idk if it's a setting you have to turn on though)
3) launch Stardew again and see if it's working now
Lots of mods are not compatible rn and will need to be updated, so best to keep posted on their listings.
Hope this helps!