I have no RAID experience, so I probably can’t give much help.
This is just a comment about the encryption.
If the partition containing “/boot” is encrypted, it is normal for the initial grub2 prompt to ask for encryption key. After providing that, you get a menu. And then, after selecting a menu entry the kernel may prompt again for the encryption key.
I’m not sure if that is what you are seeing. Your description is a bit vague.
However, I would expect the same behavior for the first boot as for later boots. And you seem to indicate those were different. So that suggests a RAID issue to me.
If you are getting a “>grub” prompt, then grub is being loaded. So I think the “/dev/sdb1” as EFI partition is working properly. Since it does not get beyond that point, something is going wrong and grub apparently cannot see your disks.
With no RAID experience, I don’t know where to go from there. Presumably your BIOS is supposed to be doing something to setup RAID disks, but that might not be working.
You should at the very least post so that your posts can be properly understood and quoted. When you put your text inside of quote of somebody else, then not only is it not clear what belongs to you and what belongs to somebody else, but this quote is also skipped when replying.
Start over and explain what you see. Because “grub menu” is exactly what you are expected to get during boot (unless you explicitly configured grub to not present this menu and go immediately to default item, in which case you should also mention this).
When someone such as arvidjaar steps in to try to help you, completely on a free, voluntary basis, and tells you that you need to give better information so arvidjaar – who is probably the one with the most knowledge to help you out in this situation – can help you …
It is generally not acceptable to respond with a snarky post. This kind of thing will not encourage anyone to help you. Also, please note, it is against our Forum policies.