Are you trying to enter self-employment income or investment income, rental income.......there certain kinds of income and certain forms and schedules that are not supported by online Deluxe, so it prompts you to upgrade to Premium. What were you trying to enter when it told you to upgrade?
The Premium edition is required if you have any type of investment sale, rental property income and expenses or income and expenses from Self-Employment.
Did you enter this type of income?
If you do not need Live Assist then see this TurboTax support FAQ for how to remove - https://ttlc.intuit.com/turbotax-support/en-us/help-article/intuit-subscriptions/remove-turbotax-live/L3WW5jwOM_US_en_US?uid=m79f31ux
When starting my 2024 return, I saw no way to decline Live Assisted (I was forced to a promo screen that required me to select the service or be unable to proceed), so it looked like I had to select the "free trial" and then go though steps to remove it later on if I don't want or need it (I don't). After several attempts to start the return, a screen came up that allowed me to opt out, so that ended up working. Not sure why it didn't in the earlier attempts - it first looked like "trial" of the service was being forced, but restarting the return seemed to work after a couple of attempts.
If you want to downgrade, this FAQ will tell you how: How do I downgrade to a different TurboTax Online product?