New Outlook shuts off Mail?

In 1995 we started our computer life with a Compaq state of the art and got MSN at Costco to go online. We've retained our MSN through the years and computers, sticking with the familiar but evermorphing Windows systems until 2011 when I won an iPad, and life as we knew it changed. We now have had 5 iPads, 4 still active throughout the house, and in 2019 I got the MacBook Pro to replace a Dell desktop in the office.

Last week or weekend I got some email from Microsoft hinting that the Outlook program(s) on our Windows computer would go defunct soon, and that I should download the New Outlook app. I put it on the old Windows laptop I retain just for its alternative options, then for some reason that I don't recall I also added it to our MacBook Pro, likely for access to some new feature(s) that intrigued me at that moment, or to have that Windows venue when the old, slow laptop's software becomes unsupported and/or too bloated for it to handle.

My issue now is that the Mail program on the MacBook stopped loading my and my wife's emails after last

Sunday. It works fine on our iPads and Android phones, but not the Mac. The New Outlook app on the Mac loads our emails very quickly, no problem. The only thing I can surmise is the Windows app is subverting the Mac's Mail in some way. One perhaps associated glitch is that I get pop-ups, displaying the internet access icon (@), saying "Can't connect to the account [Mail account name]", and that I need to enter the password(s) for my and my wife's accounts, but when I enter them they fail. I've had those pop-ups occur on the Mac regularly, but entering the password always worked. Of note on the Mailbox list column to the left of the Mail screen, there is an odd icon - a circle with what looks like a "~" in it, to the right of my Inbox name and also my wife's Inbox name. Clicking the icon causes that pop-up. What's additionally strange is that my wife's Inbox will have that icon and day-old emails, and I can go back to it later and the icon is gone and her emails are all of a sudden current.

What's gone haywire? Should I uninstall the New Outlook app because I can't have both mail options on the same device? I don't get why our account passwords don't work anymore.