My Azure Network connected with Office Datacenter. We are using Application Gateway with Private IP.
We were using Application Gateway WAF Tier Firewall Enabled but detection mode.
Under that situation, some particular user got blocked. Then we disabled Firewall mode and the issue solved.
Later that situation again arises, even firewall mode was disabled. I turn on the firewall mode and disable again, and that resolves the issue.
In order to get rid of that situation, i migrate Application Gateway to Standard Tier. After 3 days later we again faced that issue. Then i again migrate to WAF Tier, Enable Firewall under Detection mode then disable Firewall but keep WAF Tier, and That resolve the issue.
It doesn't block any particular page, it blocks the full domain even a simple HTML page not able to access.