SW tells me that it can't find the custom properties file (see yellow window), even though it does exist (see overlay window).
NEW FILE
SW opens the 'new SOLIDWORKS document' window in which there are 2 Models tabs. It does not include the templates I created and whose path I defined in the system options / file location
It looks in the "custom properties file" folder and your window shows the "custom properties" folder, in addition, the name of your prtprp file is not the same as the one requested by SW...
1°/ If I understand correctly, the directory in which the custom properties file is located should be called ' Custom Properties File' and not 'Custom Properties'.
2°/ What is the name I should give to the custom properties file (.prtprp) that SW will recognize?
Apparently your path is no longer good, go back to system option / File location and for custom property file, you have to add to repoint the correct path of your file.
And for your point 2 you can give any name to your file but the location of the files must be well filled in and you must not move it from location otherwise it will lose the link.