Opening New Window instead of new tab

Last week I downloaded the latest update for Firefox. After that I could not open websites I often use, such as etsy.com and ebay.com where I sell items. Also could not connect to Firefox Support. Yesterday, 4/19/2026 I uninstalled and reinstalled Firefox. I have box selected to open new tabs instead of new window, however, when I click on a line from my email it opens new window which causes me to have to sign-in to my accounts again, multiple times today. Also, after the latest update I cannot use my main modem network, have to use another wifi network. Also a couple of times today when I open a tab it is trying to use the primary network and pages will not load. I need help in resolving issues caused from last weeks update. I know this is very long but felt I need to tell you what is happening so you'd better understand steps to take to resolve issues. Thanks for your help.