Can you please clarify what you mean by 'writing the NC number on the nested sheet'? Does this problem arise when you turn on Marking? Does it post OK without Marking? Which Post Processor are you using?

Did you install CAMduct 2018 on the new laptop and copy your database over? Check the version of CAMduct 2018 is the same - there were service packs so to be up-to-date it should show as 2018.3. 

If you have installed 2021, did you migrate your database?

If you are on maintenance or subscription, you should look to migrate to 2021 to reduce problems with Windows 10 updates.