I am experiencing the same issue as last week too - I was able to sign apps this morning, now it stopped working. The team ID & everything stayed the same - but my iPhone complains that its "Unable to Verify App". Is ppq.apple.com really up & running?

I was about to go mad.. Tried manually installing the certificate, rebuilding the app, changing teams - nothing worked. Glad I'm not alone, hopefully apple solves this quickly.