You base URL should actually be https://ultidev/- in this case, your REST calls should have a format such as https://ultidev/rest/api-name/api-version/resource-name.
For more information you may refer to the link below:
Hey Atlassian community, I help lead engineering at Sentry, an open-source error-tracking and monitoring tool that integrates with Jira. We started using Jira Software Cloud internally last year, a...
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