@Laya
Roku Express is a 802.11 b/g/n (2.4 GHz) device. Some ISPs have changed the 2.4 GHz settings to g/n, making it difficult for Roku devices to connect on that band.
Check your wireless settings and see if they are b/g/n, and if not, change them to b/g/n.
DBDukes
Roku Community Streaming Expert
Note: I am not a Roku employee.
If this post solves your problem please help others find this answer and click "Accept as Solution."