You have written that this is your first time with UDS + UDF, and you have posted nothing about the implementation of the compiled functions with DEFINE_UDS_FLUX and DEFINE_UDS_UNSTEADY macros. This is a delicate part of UDSs and has to be checked carefully. In addition, I see no compiled function called in the "Flux Function" and "Unsteady Function" options, so I thought that you were selecting "mass flow rate" for "Flux Function" and "default" for "Unsteady Function".
The third paragraph of my previous post was an answer for both questions. Maybe it does not help, and disagreements can be solved giving additional details of the problem.
In any case, I am sure that other users will find my answer more helpful than your rude and gramatically poor comments.