My wife and I are both covered by my HSA. I know the limits for family HSA is $6750. I contributed less than that amount. Turbo tax says I have an excess contribution?

My wife and I are both covered by my HSA.  

I contributed $4750.00 in 2017 which is less than $6750.

Why is turbo tax telling me I have an excess contribution when I contributed less than the max allowed limit?