Drobo

I/o operation device error

Problem with a Drobo gen 2
I replaced a 2TB HDD with a 3TB HDD and it’s been rebuilding for 2 weeks now
Looking at the device manager in the attached Win Server 2016 it is asking me to initialize the disk which I cannot do because of an “i/o operation device error”
the event viewer says “the io operation at logical block address for disk was retried”

I own a second gen 2 (with a lot of data) which is fine, but to replace the disk while it’s rebuilding…