Error when uploading a language pack for Jira Server

[Arthur]

I followed this article to update and change a language pack: https://confluence.atlassian.com/jirakb/install-a-custom-language-pack-for-jira-server-295305642.html

I changed the .jar ending to .zip and then unpacked it. After that I opened a specific property file, changed some values and then zipped the folder back and changed the ending to .jar again.

When I upload the language pack via UPM:

jira throws this error:

Could not install the file jira-core-language-pack-de_DE-8.0.0.v20190201000500.jar. Check that the file is valid.

I also checked that I downloaded the correct version of the language pack, by checking the versions of the existing language packs in my jira instance.

So, what am I doing wrong? 

Or is there another way to do it? 

Thanks in advance!

[Nic Brough -Adaptavist-]

I have run into this when using zip utilities to re-pack files.   Try using the java command "jar" to recreate new jar files, rather than zip and rename.

[Arthur]

oh, somehow I didn't see your answer o.0 Thanks for the tip, will see if it works when I get to it