Why cant i retreive my BTH coins from my blockchain wallet I logged into my wallet on blockchain.com today. I followed the links through and saw that I had been credited with a equivalent number of bitcoin cash coins that I had been expecting.

I had a few other things to do whilst there so did those first then when I went back to deal with the BTH coins they were no longer showing. what can I do to reclaim my BTH?

btw the other things I did were to move BTC from addresses into my wallet  I also backed up my wallet and recorded a new 12 word phrase but these shouldn't has had any bearing on my entitlement to BTH
I assume by BTH you mean BCH for Bitcoin Cash.

Blockchain.info does not support Bitcoin Cash so you cannot retrieve your Bitcoin Cash as that is an altcoin. However you can take your 12 word seed phrase and use it in a Bitcoin Cash wallet software that supports BIP 39 like Electron Cash to recover your coins.