If you have a volt-ohm meter (every RVer should be carrying one of those) you should test the voltage of the coin cell. The battery cover on the remote should show you how to open it for replacement (you'll need to know how to do that at some point anyway). A brand-new coin cell should be 3.2 volts. I've seen remotes stop working when the voltage gets down to 3 volts (even though that's supposed to be the nominal voltage of the cell). It wouldn't be the first time I've seen a coin cell DOA.
The receiver should be somewhere on the outside of the camper under the awning. These multi-color RGB LED strips have a controller which is probably somewhere in the wall near where the strip power comes out (one end or the other). The optical receiver is usually on a short pigtail from the controller - should look like a tiny black button (shaped like a LED) but it may be behind an IR-transparent plastic cover so no guarantee you could see it. On pictures of your unit I've seen on the web, I would suspect that little black circular thingy near the front end of the awning on the side wall just to the upper right of the speaker. It its behind or integrated into a plastic fitting, I'd check that the receiver itself hasn't slipped out of place.
2015 Rockwood Signature UltraLite 8282WS Platinum, GY Marathon LRD, TST 507RV TPMS
2005 GMC 2500HD CCSB D/A, Curt E16, Prodigy P2, Garmin RV760LMT w/BC-20 b/u cam