Average time needed for issuing an employment visa

After 10 days asking for an update from the employer in the UAE, he says this.

What can be the possible reason for stuck?

Below is the employer's email copy:

"I hope this email finds you well. Please be advised that your visa application is taking longer than expected. At this point, we are still waiting for the Labour Approval and after that, the visa paper to get posted from the Immigration System.

Hence, we are trying our best to resolve the issue and our PRO is following up on the same.

Apologies for any inconvenience the above may have caused, and rest assured we will continue to keep you posted with regards to your start date with us."