Hi @moniski,
I understand it might not resolve your issue (as we discussed it offline), but another customer had exactly the same symptoms and the fix was to ‘Enable’ the serial port. So I am posting this here in case someone else may benefit from this comment.
RV50 has a feature to ‘Disable’ the serial port in order to save power. It has an unfortunate behavior that is when it is disabled it only receives data but cannot send them.
The setting is in ACEManager Serial->Serial Port: Enable
Please make sure that you do not operate the device in a low power mode.