I make extensive use of tags in Thunderbird and use Thunderbird on three different computers. Recently I've replaced one computer with a new one. It appears that tags put in place in Thunderbird on one of the two 'old' computers are not transferred to Thunderbird in the, third, new one. All mails are there, but the tags are missing. At the same time tags are synchronised between Thunderbird on both old computers like it used to be.

Is there anyone familiar with a solution? Thanks in advance.