The visual affect from the lamp itself was working, but the beam was not showing. I'll double check the logs in single player. Last time I checked in single player, both the visual affect and light effect were visible, but on truckersmp, this wasn't the case for the actual beam. This was the same Stralis.
Added:
Ok, in single player I used the Stralis and the headlights worked fine.
https://prnt.sc/SG7blj2GntC6
In truckersmp, I tried this and no visible beams were present. I don't know if there's an issue with my truck in mp or if this is an mp issue, but no light is visible from the lamps (the slight glow is from my light bar)
https://prnt.sc/O6AbsC_-iO5m
https://prnt.sc/HTMHwbQQrCfj