Hello there Your Mac is updated but underway of updating that pc it is had or having some error in updating on the worse side scenario of this story. On the other side it can be that new os systems on pc can normally have these symptoms of misbehavior after recommended updates. Mostly it is called reset settings after normal updates. There is nothing wrong with that but it has to be repaired then. The app and the os from that pc after being sure that you are connected to the internet can both of these programs be directly shut down by you. If these programs do not work correctly after that method it can be there that you go for the reset now of that app and also for these account s try to erase them probably and then try to reinstall them of course again into that pc. It can or might be fixed now. Also reentering passwords is a option to see closer into this after that pc is updated. If the same problems do occur even after fixing parts as security passwords and is giving issues again after reinstallation of these accounts then try to rebuild the inbox for a several times when using that pc again after uninstalling and reinstalling these accounts. Be sure that the pc has internet connections. Try to see if the thunderbird program has outrages on or for their sites.