I can’t give you a typical reason here.
Sometimes it’s not enough memory in the php.ini.
Have you tracked a lot of data as events?
Does the report work if you select a different or shorter time period? Try experimenting and try to narrow down the error.
Ultimately, you should find something about the problem in the Matomo log file on the server. You may have to configure this in the config.php.ini first.
Hi @d111
As this concerns Custom Reports premium plugin, I suggest you directly reach the Matomo support team: