There are two types of .csv files:
1. complete db tables used for moving – what you are doing
2. files with lists of custom data for photos.
The system recognizes what type it should be by the name of the file.
To be recognozed as db table, the name of the .csv file should be exactly the db table name with extension .csv.
Otherwise it is assumed to be a custom db type of csv file.
Db type files need the ids to match the photofiles that belong to the db entries, custom type files may not have the ids, the items will be recognized by the name or filenames
It is most likely that one or both of the installations (source and destination system) do not have the same db prefix.
Example: my dev site has simply ‘wp_’ as prefix (the wp default) so the name of the photo db table is wp_wppa_photos and the name of the exported db table file wp_wppa_photos.csv.
One of my other sites has ‘zcytm_’ as prefix, so the name of the file is zcytm_wppa_photos.csv
When you have the .csv’s downloaded, change the names to match the db prefix of the destination system, then upload them on the import page and they will be recognized as such during import.
By now i think my reply as quite as long as your question 🤣
Thank you Jacob, indeed both installations do not have the same db prefix. I now have changed the names to match the db prefix on the target system and it worked!
In “Moving to a different server“ is written “Note: you may have different db prefix on the traget system, no problem, you can import them as they are, do not change the filenames!” Because of that I didn’t change the filename the first time.