Issue with only pyzapp or other UPI apps too? then its KVB issue.
If only with pyzapp, check with wifi / mobile and see whethr working or not?
Remove or re-add and see whethr working or not?
Give it sometime and see whethr working or not?
Try to perform transaction like send 100rs and see whethr working or not? If sent ok, then its temprary give it some time and try again.