First, I think you should link your application as soon as possible. They are sending a lot of info through the new system.
They also sent me a generic email with the same last month with a letter with the same name as my application number, and it's not really a big deal. I think you got the same thing, with two options provided right? one was to upload the documents through the case specific enquiry tool, and the other was to mail them.
They didn't specifically say that these things are missing from my application and that I needed to submit them, it was more of a 'people usually make mistakes in these things, or forget to submit them, so verify and re-submit if you're one of them' kinda thing.
It said at the bottom of the email to ignore it if you have already submitted all the documents correctly, but in my case the RPRF and police certificates were pending, so i updated those.
Then, this week, i got a specific email from them asking for police certificates and the RPRF. and this time they gave me 60 days to submit those things. I had already uploaded those about 10 days ago, but they take about 15 days to process them, so i guess they didn't get around to the documents and sent me this email. Anyhow, i uploaded them again.
Also, after i got the second email, my ECAS updated and now it says that they sent me a correspondence that I need to reply to. It didn't happen after the First (Generic) email.
I think yours is the same.