No, you do not need to report the held ISO stock again in 2021 as long as you did not exercise more shares. You only had to claim the ISO stocks that you held in the year that you exercised the options. You may have had to pay the alternative minimum tax in the year that you exercised them. If your 2020 tax return includes Form 6251 and an amount on Schedule 2 Line 1 then you paid alternative minimum tax in the year of exercise.
If you paid alternative minimum tax in 2020, you may have gotten a credit for the tax paid. You can carry that forward this year if you are eligible to claim it on Form 8801. You can visit this section on your 2021 return in Federal > Deductions & Credits > Estimates and Other Taxes Paid > Credit for AMT Paid in Prior Year.
For more information on the taxation and reporting of ISOs, see this TurboTax article.
