Troubleshooting problem with file numbering display

[simbun]

(03-06-2022 13:48)Budgie Wrote:  Easytag has a window for setting CD but all tracks are showing 001.

How are you checking this, by selecting each file individually from the Filename tab? If you select multiple files at the same time the metadata it displays is only from one of the tracks, maybe the last one selected. In the attached picture even though multiple files are selected it's only showing values from the file 01.03.flac, which does have a DiscNumber tag of 01, but the other files don't have that tag populated.

I don't know if the Windows version is the same as the Linux version, but in the attached screenshot I've opened up a folder of FLAC files and it shows that the tag in question is 'FLAC Vorbis Tag'. When opening up a folder containing MP3 files that changes to 'ID3 Tag', so it does correctly identify the appropriate tag standard to use.

In the EasyTag preferences window, under ID3 Tags, any changes you make there will be reflected only if you're editing MP3 files because ID3 is the tagging standard for MP3, and that should be set to Version ID3v2.4 as simoncn has already pointed out.
The reason there's only an ID3 Tags setting preference and not a Vorbis one (for flac) is because the ID3 standard has evolved over the years, and some versions of that standard are better supported than others (so it gives you the choice), all the other tagging standards haven't changed, so there's only one way to do it correctly.

I hope this helps..