Hello jpturgeon,
Glad to have you connect with us here. It's essential you're able to sync your bank transactions with QuickBooks so you can manage your transactions with ease. Don't worry, I'll be happy to help from here so you can get back on track with your work.
Based on the info you've provided, I recommend disconnecting your bank from QuickBooks and reconnecting it again. The following article does a great job at explaining how you can: Disconnect or delete accounts connected to online banking. Doing this helps refresh any log-in information that may need to be re-entered again. In case you've done this already, I'd highly recommend clearing cache and cookies from your browser. Clearing cache and cookies helps fix most issues the browser may be having. Here's an article that shows you how to do this.
Try the steps above and let me know how you make out. I look forward to hearing back from you.