You have to pay CT tax on all the income that you earned while you lived in CT, no matter where the income was from. You also have to pay CT tax on the income that you earned for the time that you worked in CT, whether it was on-site at the company office or somewhere else in CT, even if it was only occasional, and even though you live in a state that has no income tax. The employer has to withhold CT on all the pay that you earned while you lived in CT, and on the pay that you earned for working in CT. If they withhold more tax than necessary, it will get reconciled when you file your CT state tax return at the end of the year.
It's not clear when you lived in each state. If you moved out of CT, did you notify the employer to change your state of residence? If they have you listed as a CT resident in their payroll system, they will continue to withhold CT tax on all your pay.
CT has what's known as a "convenience of the employer" rule that imposes CT tax on some out-of-state remote workers. But it only applies if you live in a state that has the same rule. Since NV does not have a convenience of the employer rule, the CT rule does not apply to you.
