Pvz2 bugs in worlds

Try "restore purchases" from the main menu -- it's a longshot, but possibly that could shake it loose.

If not, sadly you may have to start over as a new user. I couldn't imagine playing without the kernelpults.

I did a whole guide to stars that might be of use, but I'll summarize the "no sun" strategy.

I think the basic premise you have wrong is that you don't have to do this at the start of the round. You can spend sun and then later in the level not spend any for the required amount of time. It's much easier to establish your defenses and then do this towards the middle/late part of the round, when victory is more or less assured.

Don't wait too long, though, since the levels tend to take pretty close to a fixed time. You can extend the length of the level by digging up all your attack plants when you're down to the last 1-2 zombies, and then using plant food on a Wall-Nut or similar.