I would click the Support link at the top of this page and run through the troubleshooting section. If that doesn’t do it, and if you don’t get other help here from the community, file a support ticket, preferably from within the app while the bad camera is connected so that the logs are captured. You might want to submit the ticket right away because there’s somewhat of a backlog. You can always let them know it’s already resolved when they contact you.
How the Wi-Fi signal strength work?. Higher the number better connection?
The camera closes to my router have 45% strength but the one far from my router have close to 100%
What happen when you switch the lowest signal strength camera with the highest signal camera, did the strength of the signal remain with the location or move with the camera?
WiFi signals aren’t constant. A device further away without obstructions could have a better signal than a device nearby and obstructions. If the signal is going through a wall, then it will be weaker. If it is going through a corner of a wall, there is more obstruction. If there is an electrical field, it will affect things. If the device is too close to the WiFi radio, it may not receive a proper signal. There are a lot of variables.
You should try adjusting the cameras that are closer with power signal. Try different positions, move them away from the wall, etc…