First, a word of caution: unlike how it's advertised, Samourai is not a privacy wallet, so be prepared to give up your privacy, which defeats the point of using Wasabi. Samourai sends your xpub - which is your past, present and future financial history - to their servers, which retroactively deanonymizes the coinjoins you did with Wasabi in the past.
Assuming you don't care about privacy and you succeed, there'll still be a host of wallet balance issues on both sides of the coin. The red wallet doesn't index deep enough keys and the green wallet is bech32 only, which means if you spend with Samourai, the changes often aren't bech32 outputs, so they won't always appear in Wasabi.
If you still would like to proceed, then it should be possible as both wallet uses the same key derivation strategy. I also did the other way around (samuri -> wasabi) a few years ago and apparently this guy too :)
I can think of 2 things you are doing wrong here:
- you're trying testnet: Wasabi uses mainnet paths for testnet wallets.
- you're not aware of the BIP39 passphrase: in Wasabi your chosen wallet password is also used as the 13th mnemonic word.
If this doesn't help and you'd like to continue hacking around, you may read this great guide on restoring wasabi in electrum, which isn't the same that you're asking, but close enough and points out to many pitfalls.