I had to work with 2 different agents with Turbo technology (not the ones answering the phones; need to be transferred). After working on it for about 5 hours one day, on the next day the agent contacted me and because she continued to research the issue, found there is a problem with "newer computers display settings and Turbo Tax." She had me reset my display to lowest option (800x600?), then the window worked to I could file. I then reset back to the default.
She didn't technically explain it but said it is now being noted and most often it happens on the new computers (bought mine October 2020; HP Pavilionx360) when using TurboTax.
The agents I worked with were very helpful and continued to work to find the answer.
