After allowing the app to connect through OAuth2 (Mailcow), the initial problem while using Google Chrome was DNS, then I tried to replicate the problem using Firefox and it happened again.
It comes and goes in a random instance and random users and once I looked at the URL carefully. I found that my URL has no "/" ( forward slash) between the ".com.ph" and "api/auth" and when I added it, it worked perfectly.
Is it happening because of OAuth2 on the Mailcow or the OS Ticket?
Your help is greatly appreciated.