Just a silly question to start with: have you checked that Wifi is enabled? It sometimes happens that the aeroplane mode is activated.
Go to Budgie Control Centre > Wifi.
If the problem isn’t coming from there, post the return of this line to check that everything is starting correctly. Instead of a photo, copy the return and paste it into your message using the “Preformatted Text” button (</>), like this:
Hi My wifi is working, the problem is not there. When connecting an RJ45 cable, I realized that the connection went from Wlan to wifi. So my connection was unstable, probably because of my old wifi chip. After changing the band of my connection from 20 to 40 GHz, my connection seems to have regained stability and seems to be working fine. Thank you for your help.