I received the 1606 error on installing reckon 2018 upgrade. On research at this database the recommendation was call Reckon for assistance. Well after 30 minutes and no useful help by the consultant, I was advised by the consultant that someone would ring me back. (Who knew what they were talking about). All the consultant could do was to keep telling me to move to ON LINE, which I said NO THANKS. Well it is 24 hours later and no call back from Reckon so I decided to investigate further. The solution is to manually alter the windows registry as per the following https://support.microsoft.com/en-au/help/886549/you-receive-an-error-1606-error-message-when-you-try... I have windows 10 but it was the same process as the described windows 8 solution. This fixed the issue.