The first thing to check when a relink to a timeline won’t work is whether your timeline clips have the conform lock turned on. Default for an imported timeline is to lock.
Try selecting all clips on your timeline, right click and turn off the conform lock option.
This will allow these clips to be conformed to other media.
From there, if you still can’t get anything to work, it becomes a bit of a trouble shooting excercise.
I typically concentrate on 1 clip’s metadata, and compare it to the clip that i’m trying to link it to. What is different, and how can I get Resolve to ignore that difference.
But for sure the conform lock will stop you before you even get started.
Glenn