ISSN fetch noch working

Hello everyone,

I need to finish my Master Thesis this week. I am using Jabref 5.15 Windows.
I have created a new and empty articly entry, inserted the number 1610-2371 in the ISSN field and wanted to fetch the data. Unfortunately it is not working.
I have tried numbers like 2729-8043 or 1741-7015 but my orginal number was 1610-2371.
Always I am getting the message: error by fetchting the journal information: ISSN and/or journal name was not found in the catalogue (error message translated from German by me).

Is ISSN working with you? What can I do to repair it? Do you have a working number, which I could try?

Thanks!