I create an issue that requires approval and also create sub-tasks that can't be worked on before the parent is approved. Is there a way to have the sub-tasks check the status of the parent ticket & be placed in an "awaiting parent approval" status until the parent is approved and then they get transitioned to ready to work?
You are looking this in the wrong way, you don't need the subtasks to check for the parent status...
Create automation rule to run on "issue transition" to status "approved", this will catch all issues that are parents and moved to "approved", when that happens, run over all this issue subtasks and transition them to status "ready to work"
This should look something like this:
let me know how it goes for you.