Once the IRS has your tax return, TurboTax is out of the equation, and can’t speak to the IRS or investigate for you. Any investigation requiring human input at the IRS is probably shut down due to the coronavirus. Have you received any letters or correspondence about the delay, maybe before the shutdown?
you could try the taxpayer advocate in your state but they may have their phone lines shut down as well.
https://www.irs.gov/advocate/local-taxpayer-advocate
click on your state in the map
I received a letter stating for me to file my 2016 taxes which I did and sent it overnight to them 3/4. They said they would hold my 2019 refund until it was received. Haven't gotten anything else since then. Not sure what else I need to do.
Unfortunately, it is likely that your 2016 return has not yet been processed as the IRS shutdown around the 13th of March, which wasn't enough time to process a return that would have been received on approximately the 5th.
The IRS has not been processing any paper returns since that time and it is not yet known when processing will resume. You will likely have to wait for the 2016 return to be processed before your 2019 refund will be released.