Try to provide more information first.
So you have a Trezor Model T. You set up your HW, generated a seed, and sent bitcoins to one of its addresses. Is it correct so far?
Have you checked and confirmed that the address on your computer is correct and matches the one displayed on your hardware wallet?
What happened next?
Did you try to recover your wallet from seed and when you did the wallet was empty?
If the wallet is empty, does it show any transaction history? If you check on a block explorer, are the coins still in the address you sent them to?
How do you know that a passphrase is required?
Have you written down your seed properly and you are 100% certain of the words? Is it possible that you misspelled something?
Hi, sorry about the lack of information outright.
Yes, that's correct so far. A year ago I set up my Trezor, generated the seed, created a PIN, did a test transfer, and proceeded to transfer more (used change addresses generated by the wallet, around 7 tx). Before I closed everything and disconnected my Trezor, I looked at my Trezor Suite dashboard for a considerable amount of time and it was displaying all the coins and transfers I have made correctly.
Three weeks ago, I needed to take some funds from the wallet. I updated the firmware since I figured it's been almost a year since I've used the desktop suite. What happened next is I plug in my Trezor, successfully entered my PIN on the first try, and I am greeted with an empty dashboard. There is nothing on it, no balance, no transactions, no activity at all. Yes, the coins are still unspent and in the same addresses I transfered them to--I have a watch-only wallet for them.
Once I realize that my funds are lost, I immediately went to check my seedphrase if I'm on the right wallet or if my data has been wiped. I went through the check seed function of the Trezor, and it's the same exact seed as the one I had initially saved. It's on three different sheets of paper that I have written the seed on, and they all match, and it's the same seed that was loaded onto my Trezor.
I only ever found out about hidden wallets and passphrase when I read up on the support page and forums of Trezor. The general message I got from all the things I read there is if the seed is right and your funds are not there, it's not the right wallet.