You should be doing this whenever you want to give the receiving address to someone.
There’s no point in doing it when the wallet is imported – but if you originally did this when receiving your coins, we would at least be certain that the address that holds the coin is really generated by Trezor.
From where I’m standing, there’s two possibilities:
(a) You got the wrong passphrase. Again, this is by far the most common answer to a problem such as this one.
I believe you if you say that’s not the case 
But please think hard and consider this option too. It is possible to use one passphrase for Yoroi and a different one for Suite (or any other wallet app). There is no cross-check, using multiple different passphrases is a supported scenario, so you wouldn’t even see any kind of warning.
If you have other coins on the same seed+passphrase, and you had them at the time that you got your ADA, and you’re entering the passphrase on device, and you’re sure that it’s always the same one, it’s a strong indication that it is the right passphrase. Still, please do consider this option. Upper/lowercase letters matter, etc.
(b) Something changed in the way Yoroi handles accounts, and/or your account was not actually generated from Trezor.
Although it’s not impossible, I currently don’t see any way a problem in Trezor could cause this.
At this point, without a way to reproduce the issue myself, I can’t help you further. Please let us know if you get anywhere with Yoroi support.