can't log into gmail in either Brave or Vivaldi browsers

[esap44]

I've been trying out 2 new browsers, Brave and Vivaldi on my android tablet (ONN brand, android 11). When I try to log into my gmail accounts, I get a message that browser isn't secure, and I'm not permitted to log in. However, I can log in OK using my Firefox browser. Any ideas what's going on? Thanks for your replies. Ed