@Nickodem Watch this video (enable subtitles):
https://www.youtube.com/watch?v=skeULeTu7p8&list=PL2oNQ0AT7fx2ExiSNrfHUzga5GnogI4sh&index=23&ab_channel=Recalbox
You are probably facing some kind of incompatibility due to the different versions, as you can see in the video, to ensure that you have no problem, it is recommended to redo the scrape, to update the game lists. If you are trying to take advantage of a configuration file from an old version of the system, it is normal to have problems.
The theme is also something that can cause problems, use the default theme to test, or use a theme that has already been updated to version 7.0: https://forum.recalbox.com/category/14/themes-interface