Sorry to hear about your issues. I know it can be frustrating.
1. First, visually inspect your trailer and tow vehicle connections to see if there is any corrosion, debris or dirt. If so, correct and recheck your lights.
2. Check out your tow vehicle connections to make sure they are functioning appropriately. Use your volt meter. I've attached a wiring diagram below so you can check from point to point. If you don't have a good connection, you need to trace it back to the issue.
If you can't find the issue with these two steps, report your results so we can help you further.
