@Tereva22
If you have a cable ISP (Xfinity/Comcast, Cox, or AT&T), you may have to verify that your 2.4ghz band is configured to use the b/g/n protocol.
Your Express can only see and use the 2.4ghz band so this is first setting to look at, as well as verifying that your 2.4ghz band is actually on/enabled and broadcasting. Increasingly, these cable ISP routers are being locked down (managed by ISP, not user-editable/configurable) so may have to contact them and let them know you need your "2.4ghz Wireless Mode to be set to b/g/n".
Here are instructions for various cable ISP in case you have a model that is still configurable. If the above is not applicable to you, post back with more details of your issue, including Roku model number (Settings/System/About), your router model numer, and your ISP.
Xfinity / Comcast → ( https://www.xfinity.com/support/articles/change-wifi-mode-admin-tool-xfinity-xfi ) with a walkthrough ( https://community.roku.com/t5/Network-Wireless-Wired-Connections/Error-014-30-stuck-for-three-days/m...)
Cox → (https://www.cox.com/residential/support/managing-your-in-home-network-with-my-wifi.html)
AT&T → (https://www.att.com/support/article/u-verse-high-speed-internet/KM1046172). You can select your appropriate router from the drop down menu.
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You can try connecting to a mobile hotspot if available to you on the 2.4ghz band to verify that your Express units are capable of making a connection. This should help you verify that a network (router) setting is your culprit.
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