Likely their system is just under immense load given the bull run and new 50+k "all time high"... lots of users trying to access/use the system etc and it is not handling it well. Likewise, I imagine their support is swamped... they've always been slow to respond to support tickets and I imagine it has only become worse.

Also, given you tried a new email address and it worked OK, it's possibly also a delay caused by your email provider. You should check with them too.
The bad thing is that the major btc I have on blockchain.com are on the interest balance and this amount was not recovered with the backup.
Is this some sort of "staking" thing where you have to deposit your funds into a special account or something?

If so, then there is likely no way to recover this without help from Blockchain.com support
Yet another reason why users should be wary of using "custodial" services... as always "not your keys, not your coin"!