Welcome to the forum
A couple questions:
When you turn on the hot water at the faucet, is there good flow just not hot?
Are you hooked up to a pressurized water source, or using the water pump?
If you have good flow but not hot, then you need to find the backside of the HWH and see if maybe the bypass valve is turned "on" or partially turned. You may have to remove a panel inside the trailer to access the back.
If you have very low flow, then chances are the check valve at the out of the tank has taken a nose dive.
Do you have good pressure on the COLD side? If not then you will need to troubleshoot that.
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2012 Copper Canyon 273FWRET being towed by a 1994 Ford F350 CC,LB,Dually diesel.
Airlift 5000 bags, Prodigy brake control, 5 gauges on the pillar.Used to tow a '97 Jayco 323RKS.
Now an RVIA registered tech. Retired from Law enforcement in 2008 after 25+ yrs.