We need a bit more information. When posting questions like this, provide as much detail as possible for the workflow you have tried.
By linking timecodes, i’m assuming you mean Avid wouldn’t link to the camera clips.
What type of camera clips are you using? This is a very important piece of information.
You instead brought the clips into Resolve instead, and exported transcodes to Avid?
What file type did you use? This is very important piece of information.
Did you use the Avid preset, or make your own settings?
Did you have audio turned on in the transcoding process? I know that may sound like a silly question, but that is how troubleshooting works.
You say you put your media into an mxf workflow for Avid. Do you see both audio and video files in that folder?
How are you importing back into Avid.
The answers to these questions may help someone figure out why the workflow isn’t working.
Glenn