if you are receiving user rejected, can you check if the user is added in ISE and the entered password is correct. share live logs for this test from ISE

collect cucm trace and attach here with the call details

check if you have DND enabled in the Phone page

your call flow is not clearis this your call flowFax server--h.323---VG--FXS--fax machine?post sh run and which end are you having fax issuesif the call flow is aboveenable below and send the logsdeb voip ccapi inoutdeb h225 asn1deb h245 asn1 

you can mask the other number by using translation pattern