I could't start Photoshop without internet connection and logging in to Adobe

56440761  wrote Why this happened? What if I didn't have an access to internet?

Without Internet access, you cannot download, install & activate your CC software.  Once it's installed and activated, you can work offline when you need to.  But it's not ideal because you don't have access to your other online services like  cloud storage, library assets, custom fonts, Portfolio/Behance, Spark and more...

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Was it the first time you started a CC program on that computer?

The first time, you need to sign-in. Then you need an Internet connection each month or each 99 days, depending on the subscription you have.