I have PopClip extensions that sometimes disappear in some situations then reappear later, which can be frustrating. right now in Chrome and IA Writer, for example, tapping to invoke it on empty space only gives me the Paste+Return option, but not any of my other installed extensions, like Timestamp. Very frustrating.
I know this is an old thread but came to say I pretty much have the same problems. Not a dealbreaker so far but annoying. I do find the applet immensely useful and wish it could have many more integrations.
If you use BetterTouchTool I can recommend to map one of the trackpad “Force Click” triggers (for example with four fingers) to execute the action running the following AppleScript asynchronously in the background:
tell application "PopClip" to appear
Simple but does the trick if the PopClip bar didn’t show up after a selection was made.