Hi @Tamara_Wilburn - Welcome to the community 
I would read over a similar post : Can't connect to MongoDB Atlas - querySrv ENOTFOUND
You can try with a different DNS (like 8.8.8.8) for troubleshooting purposes but the error you’ve provided indicates a DNS resolution failure for the SRV record associated with the connection string used. Do you know if any network settings would have changed recently since you have advised it worked prior?
Regards,
Jason