Problems after upgrading to 3.18

Now I have upgraded mp3Tag to 3.18 version. I like most of it. The problem is that all my tags (made with the former versions) are gone!

I can say that because Windows Media Player is still showing me the former tags.

So do I have to recreate each and every tag of every song I have?

Please check Tools>Options>Tags>Mpeg whether you read APE tags.
If that is so, switch that option off and see whether your tag data reappears.

In general, you should remove APE tags as they cause such irritation like this.

Nope, your solution didn't work. I have just remembered I have this problem after upgrading to 3.17 version.

So, please show us the dump of the extended tags dialogue of a single file that allegedly has no tag data any more.

The tag data is a part of the file for each song, not in some mp3tag library. So if it existed prior to the update to mp3tag, it is still there. A screen shot of your library page and one with the details of one file would help to confirm this.

And how am I supposed to do that? This is not my field, I'm sorry!

here is a description how to get a screenshot:

Please select just 1 file and then press Alt-T to open the extended tags dialogue and then create the screenshot.

Sure thing! Here it is:

As you can see in the (green) title, you read APEv2-Tags with your current configuration settings.
Please re-read the first answer from @ohrenkino and try his suggestion.
How does a screenshot looks like then?

In your options, look at this setting. Toggle the APE setting in the red circle to be unchecked and update your tags. (File>Read Tag or Ctrl-T)
image

Love your rush to reply me, guys, but I still have the problem. Been properly tagging my MP3 for years now, but it seems they are gone, but the weird thing is Windows Media Player "remembers" the old tags, but if I try to edit them, they dissapear!

Nothing weird about that.
The tag data is still there - as you have shown us with the screendump that shows that you read APE tags which have precedence over ID3 tags.
Switch off reading APE tags and all the tag data that you don't see at the moment will reappear.
But that has been told by numerous participants in this thread.
Yet, you refuse to show us a screendump of the current settings in Tools>Options>Tags>Mpeg and a dump of the extended tags dialogue read with these settings.