Why can't I mark in and out points in the source panel?

[#1]

I was editing my audio track with no issues by hitting "i" and "o" in my source panel and doing insert edits into my timeline, and must have selected some option by mistake that is now preventing me from marking "i" and "o" in the source panel.  Nothing happens when I hit these keyboard shortcuts now.  What would prevent my doing this?  Thanks.

[#2]

I was editing my audio track with no issues by hitting "i" and "o" in my source panel and doing insert edits into my timeline, and must have selected some option by mistake that is now preventing me from marking "i" and "o" in the source panel.  Nothing happens when I hit these keyboard shortcuts now.  What would prevent my doing this?  Thanks.

[#3]

The only thing I can think of which would explain this behavior is that the Source Monitor is no longer the active panel.

[#4 · Accepted solution]

Thank you, but I had made the Source Monitor the active panel when trying to do the insert edit.  I saved the project, exited Premiere, reopened, and am able to continue editing.

[#5]

Yeah, that will fix a lot of weirdness.

[#6]

I saved and exited Premiere like you, but the problem happened again. I repeated the previous solution, but it happened again and much sooner. I can't keep saving and exiting Premiere every five seconds. Has anyone found an actual solution for this?