Sunbird: Problems transferring from Vista to Windows 10.

[canadac]

I have been using Sunbird Calendar with a Vista system and am having problems transferring to a Windows 10 computer.

The calendar I used had custom settings for categories and color codes. I copied my .ics file and tried importing it into a newly installed Sunbird. Most events are missing, and those that are present appear in duplicate and with the wrong category colors. The same thing happens with Thunderbird Lightning.

Is it because I changed my custom settings? How can I fix this? It is an important calendar and has too many entries to re-type manually.

Thanks in advance for any help.