Welcome from the Florida Panhandle
First off, Welcome to the Forums. We're glad to have you with us.
I have had same problem from time to time with both telephone and cat 5 locking plugs. I have always been able to remove them using a small pocket knife tip to further depress the locking tab.
SuEllyn & Brian McCabe
WBCCI #3628 -- AIR #14872 -- TAC #FL-7
2015 FC 25' FB (Lucy) with HAHA
2005 Suburban 2500 Quadrasteer (Olivia) & 2011 Silverado 3500 (Fred) with Outfitter Truck Camper (Ethel)