I do not believe that error is a mesh issue, it's rather a missing or incomplete BC issue, you might have some Boundary Condition missing (Conjugated Heat Transfer means 3 Physics: fluid, solid and heat => you need enough BC's PER physics to solve all three!) and often your material properties do not have a T component or does have one but is not reading the correct T value ...
There are many causes. Often it helps to rebuild a simpler model and check it one physics at the time.
Just now I do not have access to my WS so I cannot open your model, so I can only guess