Issue connecting Yeelight lightstrip

Hi, I just bought a Yeelight lightstrip plus and after trying to connect it to my wifi and phone, I just didn’t achieve doing it.
I tried many different things : I dis resest my lightstrip by pressing the on/of Switch for 5sec. It did work and it is properly reseted. The Yeelight app recognize well the lightstrip, and when I try to connect it to my phone it just stop working and say that there is a connection issue.
So I tried to use an old Yeelight account to update my Lightstrip firmware, so I just did the same and tried to connect it, but it also doesn’t work…
I don’t know what to do, if anyone has an idea of how to solve this, it’d make me really happy !