I've seen lots of articles across the web on this. Here's a fast way to get this fixed so you can move on to other things. Sadly, I hit this too often when renewing certificates on ADFS servers.
NOTE: This does not require a server restart.
1) Launch regedit.
2) Navigate to HKLM\Software\Microsoft\ADFS\ProxyConfigurationStatus.
3) Change ProxyConfigurationStatus from “2” (configured) to “1” (not configured).
4) Launch the Remote Access Manager snap-in.
5) Select Web Application Proxy.
6) Select Run the Web Application Proxy Configuration Wizard.
7) During the wizard it will prompt you to select a certificate. Select the certificate you were using before. Enter in some Domain Admin credentials (I don't think they're saved? Just used to authenticate?). Finish the config wizard.
9) Web Application Proxy now works again.
Works for me every time. Good luck!
