It could be your ISP. Just keep in mind Internet Connections don’t work 100% and will experience downtime.
If the issue persists, call your Internet Service Provider. There are two things you can try. The first to try would be to reset your router (or your modem, whichever you’re using). You can first try to unplug the power to the modem/router for about 30 seconds then plug it back in (not the Ethernt Cable, the power cable from the wall). If that doesn’t work, you can always try to reset the modem/router.
There can be so many reasons why Wifi Connections can be lost. There could be lost service in your area (maintenance, damaged cables, etc), or even bad weather can have a negative impact on it. If you are unable to reconnect, call your ISP, or your Landlord if you’re renting and Internet’s provided.