Videos and KMC Management site not loading, stuck in loop

https://ourserver/index.php/kmc/kmc4 is not loading, just a blank page with the circle that says “loading”
nor the videos found in:
same here, just “loading” nothing happens

this is what I´ve found in the logs, don´t know if it´s the reason:

thrown in /opt/kaltura/apps/clientlibs/php5/KalturaClientBase.php on line 912
Napping 10 seconds to allow entry Failed with message: Internal server error occurred, error code: INTERNAL_SERVERL_ERROR to digest…
PHP Fatal error: Uncaught KalturaException: Entry id “Failed” not found in /opt/kaltura/apps/clientlibs/php5/KalturaClientBase.php:912
Stack trace:
#0 /opt/kaltura/apps/clientlibs/php5/KalturaClient.php(763): KalturaClientBase->throwExceptionIfError(Array)
#1 /opt/kaltura/bin/check_entry_status.php(21): KalturaBaseEntryService->get(‘Failed’, NULL)
#2 {main}

server is ubuntu 16.04.7 LTS with nginx and ssl configured