I have two almost identical PCs with Thunderbird installed on both set up with mirror settings as far as I can see. They were both using v68 (v68.11.0?) versions and on one I was offered the v78 update about three weeks ago. It installed and works fine. That's been updated twice since and I think I'm on v78.3.2, the latest. However on the other PC I have v68.12.0 and it says it is up to date. No v78 version is being offered via the 'Help' menu prompt to check for updates and when I click on the update button under Options similarly v78 is not offered. I wondered why there is this difference. The various forum informational sources I've found suggests an extension/addon incompatibility with v78 might explain why its not being offered as an update but the PC in question doesn't use any addons. The only other plausible suggestion was that v78 is only being rolled out to specific users - sounds unlikely but maybe that is correct. I'm not keen on the idea of deleting the whole Thunderbird installation and trying to install the new updated one from scratch. It should not be necessary. As far as I can tell there is nothing wrong with it. It has updated from what it was using to v68.12.00 since. I do not mind sticking with v68.12.0 at all. But I don't like inconsistencies; its one of the reasons I set up the two PCs to mirror each other as much as possible. So if there is any obvious explanation, cause or solution I've overlooked please share.