I had issues with this upgrade and finally figured out where I went wrong.  NMRA standard for large scale is 22 volts DCC, my system is 24 volts DCC.  Soundtraxx Tsuanmi decoder is 21 volts and they have error codes on their site.  I got 10 blinks which is over voltage.
I set my system to 18 volts and all is now OK.

I do wonder how users of 24 volt only systems get around this  (LGB MTS systems are not adjustable for one)