Pretty much the title. I have tagging server here https://gtm.stastnamama.sk/healthz and I have preview server here https://preview.gtm.stastnamama.sk/healthz both shows OK but when I try to enter preview mode in GTM I get HTTP ERROR 500 Does anyone know what to look for that could cause the problem? Thank you in advance for any help.
I double checked all the settings and configurations and everything seems to be right.