permissions denied for files in the hubzilla cloud

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I uploaded file F1 in the hubzilla cloud in channel C1 and wish, that this file can see only observer (visitor), that are member in one channel group G1. I set G1 group for permission "Who can see this?" in the cloud or this file for all folder in path P1, but logged in G1 member cann't see file F1 for access with this link
and get hint "Permission denied". What can I do for provide file F1 for G1 member?

Important! Security and Privacy Settings for channel C1 is Social - mostly public.

@Hubzilla Support Forum+
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My workaround is yet - I attached file F1 in my post. Hubzilla set correct permissions for F1.