I am trying to figure out why the regular Messages/Mailbox plugin does not work on my site any longer. It does work with the Mailbox Pro plugin though, but I am hoping to stop using that plugin and just use default plugin.

Initially, I found an error with another plugin I had installed. I went through and believe I successfully manually removed that plugin. The errors relating to that plugin have gone!

But there are errors present now appearing directly connected to the Mailbox plugin that I do not understand. I will attach a screenshot.

Does anybody have any idea of what this might be referring to and how to help me correct it, please?

Thank you.