Hello! I see you're having two issues: the Twinkly app is not starting properly, and when it does start, you can add playlists only to patio lights but not to other lights. Let's work through these step-by-step.

First, about the app not starting:
1. Please try closing the app completely on your Mac running OS X 10.15.7. You can do this by right-clicking the Twinkly app icon in the Dock and selecting "Quit." Then restart it. This sometimes clears temporary glitches.
2. If the app still doesn't start, try restarting your Mac. Sometimes a fresh system boot helps.
3. Make sure your Twinkly app is updated to the latest version compatible with your OS. You can check the Mac App Store or official Twinkly website for updates.

For the playlist issue where you can add playlists to patio lights but not to others:
1. Are the other lights grouped or linked together in the app? There is a known limitation where playlists cannot play across joined or grouped lights simultaneously; the playlist might only apply to one group at a time. You might need to start playlists manually for each group separately.
2. Ensure that all your Twinkly devices are connected properly via the app. Go to Menu > Devices and check their status. Make sure the app recognizes all lamps distinctly.
3. If your lights are grouped but you want the same playlist to run on multiple groups simultaneously, this may require starting the playlist on each group individually, as the app currently doesn't support applying playlists automatically across multiple groups at once1.

Could you let me know if the app refuses to start entirely or if it just takes a long time to open? Also, about the lights, are they set up as multiple devices or grouped in the Twinkly app? This will help me guide you better.