Welcome, Cab308. I believe you are referencing the Barrel Latch. It can get very stiff over time since it is seldom cleaned thoroughly. I suggest you spray some WD40 into it from the Trigger Guard then get a hard nylon (plastic) instrument to apply as much pressure as possible, pushing it into the Trigger Guard. Take care not to mar the finish doing this.
Just want to also be sure you clear the Chamber, cock the Hammer, and put the Safety ON before attempting to move the Barrel Latch. When the Latch is depressed, you have to move the Slide forward and up to disassemble.
Let me know how you make out.