I have two TCL Roku TVs that i purchased from Costco the same day. Both are 50". Both are TCL Model 49S403. However, one has a Roku TV Model number of 7130x and software version of 9.2--can connect my internet to it. The other has a Roku TV Model number listed as 7101x and a software version of 7.5 I have tried connecting to the internet, and i get a prompt that there is a software update, but I am unable to ever connect back to the internet after I follow all steps. I tried downloading the software and uploading via USB, followed those steps, and nothing works.
Have you tried contacting TCL support yet to inquire further? I'd suggest starting there to see what options or suggestions they can provide. Each Roku TV manufacturer provides direct support for their products running the Roku OS.