Error 504 Gateway Timeout

[KatiaSisHost]

Hello, a while ago I had this problem and I was able to solve it, but a few days ago I had to reinstall the OPNSense, and I have the same problem again, but I can not find the solution.

I have a WebServer under DMZ with OPNSense, everything works fine, but if my web takes a while to load, it throws 504 Gateway Timeout ERROR ...