I replaced my computer. I followed these directions: Moving Thunderbird Data to a New Computer https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer I installed Thunderbird on the new computer. I opened Thunderbird and canceled configuring it. I copied the Thunderbird folder from my old C drive to the new computer to this folder: C:\Users\bkoop\AppData\Roaming\Thunderbird I opened Thunderbird. All my 6 email accounts were listed. I had to click on folders for the message total number to appear. Several accounts received messages but no messages were retrieved for my main email account: bkoopers@irbl.net The 20 to 50 emails that I would normally receive after I powered off the old computer yesterday and up until 5:30 pm today when I setup Thunderbird on the new computer are not there. I logged into the webmail website for my bkoopers@irbl.net account. All emails not retrieved by Thunderbird should be listed there but there were no emails in the Inbox there. I had somebody send me an email. It appeared at the webmail screen. I selected "Get messages" for that email account in Thunderbird and I retrieved that message. A few minutes later, several other new emails arrived in Thunderbird in that email account. The emails from the previous 24 hours are just not there. In addition, I have three Add-ons that I had installed: Quick Folder Move ReFwdFormatter ReplyWithHeader They are listed in the Add-ons screen but they do not work. They do not say they are incompatible with Thunderbird v155.9.0. Do I need to remove and re-install them? Can anybody tell me what happened to 24 hours worth of new emails from yesterday and earlier today?