Hi John,
I think Ali_E1 and ryane77 have both misread your issue.
Their replies are responding to an issue involving merging two adjacent cells in a Table.
BUT your issue is NOT about merging cells.
Your issue involves attempting to place a merge field in a Pages document to get data associated with a specific person or entity from a source document (such as a Contacts record or from a list in a Numbers or Pages Table) and insert it in that merge field, thus merging that information into the document containing the Merge Field, a process sometimes described as mail merge.
Not an issue I can help you with directly, as my current version of Pages does not, to my knowledge, support mail merge or merge fields.
My goal in posting this is to attract the attention of someone who is familiar with mail merge in Pages, and who may be able to provide you with a solution.
Meantime, you might take another look at these three articles in the Pages User Guide for Pages 12.1:
Add, change, or delete a merge field in Pages on Mac
In Pages on your Mac, create custom fields that populate with information from sources like Contacts or a spreadsheet....
https://support.apple.com/en-ca/guide/pages/add-change-or-delete-a-merge-field-tan1ef722d07/12.1/mac/1.0
Populate and create customized documents in Pages on Mac
In Pages on your Mac, populate merge fields with a Contact card, Contact group, or Numbers spreadsheet.
Populate and create customized documents in Pages on Mac - Apple Support (CA)
Add, change, or delete a source file in Pages on Mac
In Pages on your Mac, use a Numbers spreadsheet as the source information for merge fields.
Add, change, or delete a source file in Pages on Mac - Apple Support (CA)
Regards,
Barry