The common reasons:
1. Using the Wrong Spectrum Band
if you want the fastest WiFi speeds, you should always use the 5 GHz band
2. Using the Wrong WiFi Channel
You can change your WiFi channel by accessing your AP’s settings page and choose the best channel.
3. The AP is in the Wrong Place
You will have better coverage if you place your router in a central location rather than in a corner.
4. The AP version is out of Date
Change out your old AP to Reyee WiFi6 APs(RAP2260G/E, RAP6260G)
5. The network drivers are outdate.