Design - prevent multiple nesting in function
Use optional instead of null. I wrote an article about avoiding nulls if you are interested.  
Use early returns to avoid nesting


If !reader return [status: '50', message: 'READER NOT FOUND']

If !userSettings return...
Rest of the logic



I prefer to avoid nulls,so I would choose to call save with failOnError=true and it will throw exception instead of returning null when save fails. 
I assume  you want any exception to return [ status: '60', message: 'error'], if you use save with failOnError=true then the error is handled in one place only. 
add validation for params.isAccessIn. If by mistake it is nor true or false, it is better to throw error than do something the client didn't intend to. 
Maybe you should be more flexible with params.isAccessIn and compare strings without case sensitivity.