URLs with the type “.” Are not supported.

Please read the following user tip and restate your question/problem in detail: 

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Give us an example of the URL you're having problems with?

What model and year Mac do you have?

What browser are you using?

Connect the two Macs how? SMB? AFP? WebDAV? Something else?

What’s the (apparently failing) URL you’re trying to use?

What is the macOS version on the older Mac?