*I've done the factory reset.* mac address displays all zeros and it will not scan wireless networks. I tried to put in private network but it will not connect to our wifi that way either. Only had this device since August 2021 and it's already giving me these problems.
Are you powering your Roku Express with the supplied power adapter through the wall or through your TV USB power port? Try using the wall power unit if currently using TV power port and restart your router as well.
If you are currently using the wall power, then the NIC (network card/chip) inside the unit has most likely failed (or at least as encountered an internal issue) if wireless MAC is showing all zeros (0:0:0:0:0:0).
You can view the settings from Settings..Network..About
If you are sure it is the MAC address showing zeros (0:0:0:0:0:0), and not the IP address showing zeros, (0.0.0.0) and you have verified proper power supply and restarted router, then you should return for warranty replacement. (https://support.roku.com/article/208757058)
Had the same thing just happen to my Roku. I’m not happy with the lack of support to fix this problem.
@Whitelion, if your MAC address is all zeros the fix is to replace the faulty device entirely. If it's still under warranty:
Step by step instructions for returns and warranty replacements | Official Roku Support