Hi,
I found what is causing the problem.
I followed the above instructions but the problem was still there.
I tried different things and I realized that the problem is with the Greek language.
So if I change the website language to English or if I just change the user language to English it works properly.
Then I tried something else, I followed this path …/wp-content/plugins/woo-advanced-shipment-tracking/lang/ and deleted the files for the Greek translation (but used as site and user language Greek) and everything is working as it should.
So, I decided to check the translation files and I saw that there were a ton of errors. I then fixed the translation file and uploaded them again in the …/wp-content/plugins/woo-advanced-shipment-tracking/lang/. Now everything works properly.
No more errors. Everything is fixed.
I submitted the new language files on your website.
Consider to add them on your next update.
If you mention on your site the contributors, then please mention BigDrop.gr