Is this genuine?

Received this email this week, just a bit strange as all our documents went to the company who deal with the applications, also thought if any paperwork was missing that they would contact us? We tried to reply to the email but our email could n't be delivered

Yes genuine they are asking for the information in the e mail.
I would edit out your email address

We keep trying to reply to this email as it suggests but the email keeps failing

It will it’s a non monitored e mail address that send only but does not receive avoids complication of who sent what where!
If you don’t have an alternative e mail address which I doubt you have try uploading the wanted documents as you did when you sent the first batch.
Not sure you can re-edit the uploaded once the application is in but try as the e mail you have posted suggests you do need to upload

I would say that we have already sent 80‰ of what they are asking in the original up load I'm not sure why they are asking for 24 months of bank statements when we had already sent most of them.

So we can't reply to the email they have asked us to reply to and the app we originally used to upload to won't let us upload anymore paperwork

best I can find to help you!
Call us on the phone number included in your UKVCAS confirmation email. Send an enquiry via our Help and Support page. Alternatively you can use 0844 892 0232 (inside the UK) or +44 844 892 0232 (where available from outside the UK) – these calls cost £0.04 per minute plus your provider's access charge.

I would use the phone as quicker get who you speak to name, give them your GWF number, application date, name and then once logged follow the call up on Sopra Steria visa help and support page.