Sorry to hear you are facing problems to create sub-tasks.
The only permission needed to create sub-tasks is the create issue permission independently of the JIRA application you are using, so I believe you might be facing a different problem.
Can you please let us know what are the changes you mentioned?
Additionally, are you using JIRA Server or Cloud? If you are using Cloud, are you using a classic or a next-gen project? The sub-task issues are not available yet on the next-gen projects.
In advance, I suggest you check if your sub-tasks are enabled on your instance by navigating to JIRA Setting > Issues > Sub-tasks
Let us know if this information helps.
For JSM June Challenge #2, share how your non-technical teams like HR, legal, marketing, finance, and beyond started using Jira Service Management! Tell us: Did they ask to start using it or...
Connect with like-minded Atlassian users at free events near you!Find an event
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no Community Events near you at the moment.Host an event
You're one step closer to meeting fellow Atlassian users at your local event. Learn more about Community Events