Thunderbird is one of the best email clients to access your IMAP or POP email accounts. Sometimes, the Thunderbird mail app not syncing on your email account and as a result, you won’t be able to access your latest email messages. In such cases, you have to check if all the settings have been configured correctly in Account Settings.
The functioning of IMAP sync in Thunderbird during various scenarios are given here to fix Thunderbird mail app not syncing issue.
If you have a stable Internet connection, but the Thunderbird client is not synchronizing, perform the following steps.