"Failed to add entries to the database"

Hi!

I’ve been using your plug-in for a while together with Pinboard theme. Currently, I’m in the process of switching themes to Custom Community, but can’t get your plugin to work. I can’t seem to add any information, as I just get “Failed to add entries to the database”. Never had this problem before.

What to do??

https://www.ads-software.com/extend/plugins/weekly-class-schedule/