SapphireSharon Please try accessing the Sims 3 Store site through Firefox, in a private browser window. If that doesn't work, try Edge. And let me know what happens when you try.
The launcher can be finicky at times, and it also doesn't work well when the username or password contains special characters, for example & or !.
What exactly did you buy? If it's a stuff pack, for example Outdoor Living, you need to install it through the EA App (Sims 3 > Manage > Manage add-ons). Store content does need to be installed through the Store site, but you don't need to sign into the launcher first.
I use edge and I tried using crome browser nothing works. EA games closing my cases without helping me could it be I have Seagate and when I hooked it up it doesn't have a app for it so can't access it. Downloads came with it was for adjusting colors on it I'm not sure how to access it and I think my games are on it instead of my laptop!? Not sure. First time I ever had one nothing comes with instructions anymore. Yeah I tried downloading outdoor life stuff pack through EA app and went to 96% then error saying that it can't download. Makes no sense.
