Thank you for reaching out to the Community. We can check your payroll settings. It could be one of the possible reasons why it changes from CT Quarterly to CT Income Tax.
Here's how:
Click the Gear icon, and select Payroll settings.
Press the Pencil icon, and check the frequency schedule.
Made any change if needed.
Tap OK once done.
To learn more about the Payroll Tax Compliance, please refer to this link, and select Connecticut.