What can I do if my ex-wife is not cooperating to renew the visa of her and our son?

I am legally divorced since 2015 in the UAE and paying sustenance to my wife for our son (15 years).

Son is under the sponsorship of my ex and she is not renewing her and my son's visa. My son has no visa or medical insurance.

I am willing to sponsor my son however, my ex is not cooperating. My ex-wife is not working or earning either. What can I do?

I want to protect the legal status of my son and have proper health insurance for him.

Which government department can I report this matter to?

Your advice will be appreciated.