Hello! So I've ran out of ideas to try and solve this issue and hoping you talented people can offer me help!
We're using Jira Service Desk in the Cloud and we had an internal staff member create an issue on behalf of a client of ours in our Jira Service Desk instance. They created it and had marked a client of ours as the "Reporter".
This client already had an account with us and currently DO have a ticket made at a later date assigned to themselves in our service desk instance that can be seen by viewing their currently open issues.
However the ticket giving us difficulty does NOT appear on their currently open issues and is not accessible to them.
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Things we have tried:
Clicking this "Share this issue by emailing other users" button and then emailing the client who was assigned as the "reporter" did not work.

They received the email but when they select the link they ran into this issue:
"By using the link given in this email chain, I am taken to site stating “incorrect request type”." alongside this image."

I am at present failing to reproduce this issue and so I'm not sure quite what to do here, and attempts to resolve the issue thus far are failing.
Help would be IMMENSELY appreciated
!
Thanks and bless!