Application Link Confluence to other Jira-Servers

Hi,

we newly installed an installation of both JIRA and Confluence.
If I try to create the Application Link at the Confluence Instance, the UI shows me the following Message (also appended as a screenshot):

[Exception... "" nsresult: "0x805e0006 ()" location: "JS frame :: https://its01.koramis.de/s/0f1aa721407b8b249d74bf59dc0ea5cf/de_DE/5501/a39771cd4bb7ab00a226a7ea8d6dd65e64226a7f.1/7/_/download/superbatch/js/batch.js :: .send :: line 165" data: no]

If I reload the page, the entry is there but there...but not really linked.
It also appear when i try to link Confluence->Stash, Confluece->Bamboo.

The other way around, there seems to be no problem for linking.

Thank you in advance
Philipp