Could be similar to, or different from, issues on this thread:
I’m not the pro, rather @jeffeb3 and others are.
Some things to check: baud rates must match. Wiring.
In the event it might help, here’s my TFT firmware that I’ve been asked for several times and which I have shared: As posted over there:
I have received several prior requests for my TFT firmware, and I had forgotten that late last year I uploaded it to my website to make it easier to share. Here’s the link!
http://design8studio.com/files/Firmware-for-my-BTT-LCD-control-screen-TFT-3.5-E3-v-3.0.zip