I can't not change the Issue Type of a ticket

[Nguyễn Minh Tú]

Background: We have all issue types in the project: Bug, Epic, Milestone, Story, Task, Sub-task. 
Step 1: I create my own project
Step 2: I create one Task ticket for that project
Step 3: I click on the Issue type of that ticket to want to change it from Task to Bug 

It shows `You can not edit this issue type in this project`. When I bulk change for that issue, I show the Task/ Milestone issue type only.
It recently happen, a few months ago I can do it normally. What should I do? Is this a bug?

[Nguyễn Minh Tú · Accepted solution]

I found the root cause:

- Not adding field `Issue Type` into the current Screen of the project