Solo401K, does turbotax wait until your entire return is completed. I am entering my contributions, but I do not see my tax liability changing.

If you have entered all of your Sch C income and expenses then the 401K contribution should be populated correctly ... review the return to see what is happening ... do NOT just look at the idiot Meter.  Most likely your taxable income is zeroed out so you owe no federal taxes  but  you still owe the SE taxes.