Events list is missing from Events Webapp part

Hello,

 

We have an event web app on our intranet site with 3 categories.

For some reason though, when in "see all events" view, when a category is clicked for filtering, it just shows a red bar on the top of the page, which says: "Can't open this Events list. It may have been removed, or there may be a problem with the link you are using to access the list." 

Any idea how to fix this issue?

Help would be appreciated, thank you very much!

 

Here are a few photos.

event categorieserror