How can I Get an Issue with REST API call

[Hostvisors]

I am integrating jira for the first time.I have provided the Basic auth (user and the token is valid), I am trying to fetch an Issue of a perticular project "Reservations" by key but upon request receive this message .

"Issue does not exist or you do not have permission to see it."

Tried to fetch all of the Issues of "Reservation" project by jql as can be seen in the 2nd Image. 

Please guid me what mistake I am making.

[Florian Bonniec]

Hi

What API call do you send?

The user you have provided need Browse permission on the "Reservations" project. You can try to log in into JIRA with this account. If you can see it, the issue is porbably somewhere else.