Neither of the above answers are correct. If the forms aren't ready, TurboTax online won't let you attempt to transmit - it will stop you before you get there and tell you it can't be transmitted, and it will provide a list of the forms that are not finalized and the dates they should be ready. It will also watermark the forms as not final when you preview the return.
I filed my federal return without issue on the 22nd and it was accepted by the IRS on the 23rd, but I'm getting the same error on my MN state return and have for several days now, and all my forms are available and finalized. It originally stopped me and said a bunch of MN forms weren't final and would be ready on the 23rd (no M1PR, I don't qualify), and the state forms were watermarked in the preview of the return. On the 22nd, this was no longer the case - I was not getting any notification the forms weren't final and they were no longer watermarked, and it let me go through all the way to transmit, so presumably they finalized the forms a day earlier than planned. Only then did I start getting the 'Tax Year 2024 transmissions are not available' error and I've been getting it ever since. And yes, Chrome, Safari, clear cache/cookies/etc. makes no difference.
Basically, if the forms aren't finalized, TurboTax will never even let you attempt to transmit and see the error the OP and I are seeing. My suspicion is that this is actually an issue with MN not 'turning on' the filing ability until Monday the 27th. But yet the IRS also isn't 'accepting' returns until the 27th and yet I was able to transmit it on the 22nd and have it accepted on the 23rd.
