You get this error when searching Youtube sometimes. I believe the reason for this error is the addon uses an API key with a limit on the number of queries for each day. When a lot of users have done queries and have reached the limit, you can no longer search for anything.
One solution is to register an API key to your account and sign into Youtube. However another better one is to use a Smartphone app like Newpipe, which once you’ve found a video you can then play it in Kodi.
Retropie is an excellent addition to the software already available to the Raspberry Pi. It comes with a handful of emulators out of the box but is capable to run many more. The way to use them is a bit convoluted. First you execute the retropie cfg script and install an emulator you want from there e.g. snes, PS1 etc.
Now even though the emulator is installed, it won’t show up in emulation station. For that you have to put a ROM with the correct extension in the emulator folder. Then you can select the emulated system from emulation station.