Receiving “Cannot load flamingo_inbound.” error

I am receiving the “Cannot load flamingo_inbound.” error message when trying to manipulate messages on the Inbound Messages page. (Either delete, mark as spam, edit, or even just to view the messages.)

I am using Flamingo version 1.4, WordPress 4.6.1, NOT using WooCommerce.

Site URL: https://fxbgoffices.com/

I have tried uninstalling & reinstalling with no luck.

I found the support thread here, but it is from more than 3 years ago, and the code changes suggested in the thread didn’t seem to apply anymore (it was based on a previous version, and it looked a bit different from my files, so I was unsure about making the edits).

Any help would be greatly appreciated. Thank you!!