If you don't want to buy a replacement light, pop one out that works and plug it into the one that doesn't. See if that resolves. If so = new light for the other side.
2004 Supra Launch 22 SSV
5.7L Indmar Assault
"One More Hour"
Most trailer light issues that i run into are actually grounding issues.
Korey Morris -
Sold to Arkansas: 1986 Supra Saltare
Current: 2018 Moomba Craz