Access denied to website in safari and Firefox on iPad and iphone

Hello, I have been trying to troubleshoot this issue on my iPad and iPhone for hours with no avail. When i log into a site I get access denied on this server error. Things I have tried are:

clearing browser history and cookies and restarting iPad / iPhone ... still same error

checking if I get same error using cellular .. same error

reseting network connections .. still same error

reseting modem ... no change , still error

turning off VPN .. no difference .

used another device in household. Gives same error.

I can access site to log in , but instead of logging me in I get access denied on this server error .

any help would be greatly appreciated as I need to access this website .