Welcome to the 'Community.FamilySearch" Forum.
I am just another 'lowly' User/Patron ...
Just in passing ...
And, not in response to any "Instructions" ...
Just in Relation to "Records" (ie. a "Sources") in "MyHeritage_com" ...
IF, you find a "Record" (ie. a "Source") in "MyHeritage_com"; and, want to be able to "Attach", that "Source", to an individual/person, in "Family Tree", of 'FamilySearch'; THEN, the URL for that "Source" MUST have:
Where, [PID] is the 'FamilySearch Person Identifier' (PID) of the individual/person concerned
at the very end of the URL.
Otherwise, there is no ability (ie. Link/Button) to transfer, from "MyHeritage_com", to 'FamilySearch'.
Such can be added, if it is not there; and, you have to "Refresh" the page/screen, to get it to "Synchronise".
More often than not, the INTERFACE between, 'FamilySearch'; and, "MyHeritage_com", can be somewhat 'cantankerous' ...
Sometimes, for short periods of time, the INTERFACE between, 'FamilySearch'; and, "MyHeritage_com" may actually be down, in such cases, no amount of trying will work, it is just a matter of waiting, until the INTERFACE is back up and running.
Especially, if either, 'FamilySearch'; and/or, "MyHeritage_com", are working on their individual "Systems".
Oft, it is a matter of just preserving; and, trying again (and, sometimes, again), until things, are back un track.
Just my thoughts.
I know, that this may not help/assist; but, I hope, that this may provide you, with some additional, insight; and, perspective.
ps: When everything IS working properly, it is great; but, what a nuisance, when it is not working properly.