Modules of deprecated functions automatically get deactivated during app installation.
Read in the function's documentation how to replace the deprecated function.
If you still want to use the deprecated function, you can activate the corresponding module manually in your "manage apps" section of Jira.
Here is an example for the Number Compare Validator:
Overview of deprecated functions
| function | replaced by | enableable | enableable until |
|---|---|---|---|
| Number Compare Validator | Field Compare Validator |  | 30.06.2020 |
| Number Compare Condition | Field Value Condition | | 30.06.2020 |