I figured out why after buying multiple different remotes, I could not get any to pair, and I wanted to share my solution which is not your typical issue!

Purchased a Toshiba 32V35KU FireTV off Facebook Marketplace, was told Remote hasn't been working right recently but can use the app. Got it home, remote had dead batteries, replaced and it worked. Went to setup/enable WiFi but it would not turn on. Remote would double click on select but I found if I press it then pull the batteries quickly, it will single press. Could not get WiFi turned on, thought possibly it is a setting issue, performed a factory reset to remove previous owners amazon info and settings. Come to find out, the remote will not pair to the TV. Purchased multiple different remotes from Best Buy and Amazon, did a ton of research trying to find any info on this TV aswell as what remote is compatible with what, not much info is out there or was helpful.

I was about ready to just toss it off my balcony and buy another, then I thought back to the WiFi issue.. Maybe a bad WiFi/BT module?

Opened up the back cover, searched up the part number and found it online for about $20. Upon looking further into the board and everything, I found a pin that was not seated all the way in. It's the purple wire from the main board to the WiFi/BT module, the far left in the picture(pic was after I fixed it). Made sure it was seated all the way and reconnected it, plugged the TV in, turned it on, every remote I bought instantly paired no problem!

Quality Control at its finest, never will I buy a Toshiba product again. I hope this eventually helps someone out there.