Hello Dan, 

Thanks for reaching out! It's difficult to say exactly why your tomatoes are not ripening, but here are a few thoughts and helpful articles: 

1. The optimal temperature for ripening green tomatoes is 68-77 degrees F. Temperatures outside of this range, especially for extended periods, can slow down or halt the ripening process. I have been traveling outside of MN for the last few weeks, but if temperatures have been hot, it may have impacted the ripening of your tomatoes. 

2. It may be beneficial to remove tomato branches that are not bearing any fruit. This will direct the plant's energy into ripening the fruit, rather than trying to produce new blossoms on these branches. 

https://www.purdue.edu/hla/sites/yardandgarden/tomatoes-not-ripening/

https://extension.umn.edu/vegetables/growing-tomatoes

I hope this helps - good luck!