Hold tight. Amended returns take FOREVER to process; I think you are lucky that it is marked as received as that can take weeks sometimes. The IRS website admits it can take up to 16 weeks to process, but I've heard of a lot longer especially in the last year since the pandemic started. The backlog is 3x larger than it was in 2020 and 4x larger than 2019.
We started getting that message several weeks ago and then last week it was processed and we got our refund! Our amended return had been marked received on 2/16 so it took a long time.
It also triggered our advance child tax payments status to change from “not receiving advance payments” to “enrolled in advance payments.” We also got our stimulus this morning.