Page not found

When I click on an event in the calendar or list, the system tries to open a page like
http://alan-arif.de/blog/ecp1_event/nino-girsiashvili-allewelt-ensemble/
(everything non-fat is specific to my page but the fat bit should be generic) but it cannot find that page.
This might help: I had the same problem with another calendar plugin (which I liked far less than yours, but which also uses post types similar to yours), and they present several solutions on their website:
https://theeventscalendar.com/knowledgebase/fixing-http-404-errors/
“Flush permalinks” did not work for me (since I had it already hat way), but the “Try pasting this snippet in your functions.php file” bit did solve my problem. So maybe there is a smilar way to solve the issue for your plugin.

https://ww.wp.xz.cn/plugins/every-calendar-1/