Multimode SFP works while Singlemode SFP does not

I hope this isn't too low level for you guys but I have been around trying to get this resolved and was hoping for a bt of input.

I have an HPE OfficeConnect 1920s and our CDW rep recommended "compatible" C2G Singlemode SFP Transceivers which were $50 vs the HP branded transceivers which were $500. I can't for the lfe of me get the transceivers to work. For the heck of it, I test an Extreme Networks Multimode transceiver and it worked almost immediately.

Is there something special i need to do to get the Singlemode transceiver to work or are the C2G transceivers just to cheap to work with my switch?

I submitted a support request to HPE and their boilerplate answer was to make sure I have HP branded transceivers.