We had an issue today where a user got locked out of the RemoteApp that they would normally access without issue. They got an error message that read:
As a security precaution, the user account has been locked because there were too many logon attempts or password change attempts. Wait a while before trying again, or contact your system administrator or technical support.
It reported error code 0xd07 and looked something like this:
The solution was to remove the user from the application group that included the RemoteApp, using the Remove-RdsAppGroupUser command. You'll need to do this from a PowerShell session (see here for more).
If this doesn't work, here's a few more things to try: