SO Actually I have made a Dynamic Site where users login.
But some of my users said sometimes they fail to login.
But sometimes in incognito, it works.
I checked the Error Code was -Failed to load resource: the server responded with a status of 503 (Service Unavailable) wpadmin ajax
I know it errors at the server level in PHP. Presently i use 7.3 should i upgrade?
or is it mod security error or something else?
Please help me fix this 