Unable to use Family Sharing

Check here -> Apple Media Services Terms and Conditions

Legal - Apple Media Services - Apple

• Family Sharing Rules: You can only belong to one Family at a time, and may join any Family no more than twice per year. 

So, your account will be able to use Family Sharing again in xx days.

If i remember correctly, your screenshot says 68 days, correct me if I'm wrong.

Get more support -> contact Apple -> Choose your country or region - Official Apple Support

or Call Apple in your region see: Contact Apple for support and service

Contact Apple for support and service - Apple Support

Your screenshot was likely removed because it included personal information, but without the screenshot your question has absolutely no context. Either re-post the screenshot without any personal information included or please provide a more complete text-based description of when you are seeing your message and its exact wording.

The message on your screenshot is clear.

So waiting is the only remedy.