I don't understand why this is happening now. This was never a problem.
I have tried the following without success:
Reset network settings.
Make sure the date/time are correct — they are.
Reset my internet modem.
Sign out of Apple ID for iTunes, then sign back in.
What worked was turning off my Wi-Fi.
Here's my problem with that though: why would Apple make you turn off your Wi-Fi for you to update your apps and software, or even to sign in using an Apple ID? Why do I need to use my Mobile data to update my phone?
Apparently it's because of my DNS. When adding DNS 184.108.40.206 and 220.127.116.11, everything started to work. I replaced some IP address with the 18.104.22.168.
Why was this happening? Why was there a different IP address in there? Why now? never had this happen to me in a decade.