Found this solution in another thread. IT WORKED (and I had already tried all other suggestions)! You'll need to bypass your WiFi router and plug your computer directly into your modem. Instructions from @nothanks23 : unplug router's power cord to turn it off; de-attached the Ethernet cable that connected my modem and router; unplugged my modem's power cord; re-plugged it in to reboot it; connected my laptop to my modem via the Ethernet cable (I had to use a USB 3.0 to Gigabit Ethernet Adapter since my laptop does not have an Ethernet port). Once that was successfully connected, when I started Turbo Tax, there was a new update to download. After installing the update, I was able to efile my federal taxes.
