4 outlets in abedroom show power with a tester, but when I plug something in the tester light goes out. 1 outlet in my living room does the same thing. 1 outlet in the bedroom is connected to a light switch and has no power showing. All outlets were changed to new ones still no power. All these worked in the past and the breaker isn't tripped. Can you help?

Check the grounds and neutrals in the electric panel. Then check any exposed J boxes.

Check for open neutral neutrals switched If you want for about $10.00 big box store has a great tester Its square looking has light codes and on side it shows what lights lit means you just plug in an outlet Just cause there power does not mean a complete circuit The tester can start you off and point you in the right direction and chase it from the panel box or vice a versa . Lose wire nut. Check Junction boxes on circuit if there are any.
Hope this helps
Happy Holidays Signed boat