Issues with plugin-manifest.json

Issues with plugin-manifest.json

Hello community,
I just began creating an extension for our company, as we customers, which write e-mails to different departments. So now I want to create a widget, which checks, if the customer has more then one open ticket.

The problem is, that after I started configuring the plugin-manifest.json, I can't test the widget anymore. It does open instantly when I load https://127.0.0.1:5000/ instead of asking me to confirm to access a unsecure site. And when I refresh my page on Zoho Desk, I see in the terminal, that the ressources are loaded:

OPTIONS /plugin-manifest.json 200 1.742 ms - 8
OPTIONS /resources.json 200 1.044 ms - 8
GET /plugin-manifest.json 200 2.405 ms - 482
GET /resources.json 200 5.442 ms - 2

But the widget doesn't show up. Attached is the plugin-manifest.json and widget.html

When I try to validate with zet, I get this error:
PluginManifest file validation :- 
 ==> Only the Zoho Services related connection should be in zohoAuthorisation.

Which surprises me, as in Sigma.Zoho.eu, I only added Zoho Desk as the connection. But also when I remove the whole connection, I can't see the widget.

Attached is the widget.html.

I have the Zoho Desk Advanced Plan, if that is relevant. Does anyone know, what I am doing wrong?