Service tax challan paid showing does not exist

while filling ST 3 return for quarter1 of F. Y 2017-18, against service tax paid details, the challan number is being correctly entered. but it is showing that challan no does not exist or not matching with registration no. i have checked the challan and everything is in place along with the registration no. I have also checked challan status enquiry and found my challan is very much there in site and as well as with paid status. please suggest me what to do as my return is still pending. without the challan being accepted i m in dilemma.