I don’t have your audio interface, so all I can do is offer some blind observations…hope something helps!
First of all… In that YouTube video you posted, you didn’t quite follow the instructions explicitly! According to your third screenshot… you still have the default stereo input enabled! The video suggested you use mono channels instead! That could be significant if your particular interface doesn’t have the ability to send a combined (single) stereo signal, and Cubase is configured to accept that type of stereo signal ( I don’t know this for sure… just a place to start looking). That error message you are getting suggests that your hardware communication is being blocked by something misconfigured on your system, so let’s examine some other possibilities! I have seen this message sometimes when I’m using Reaper, and I have set the sample rate to something different than the autoloaded song in Reaper while using Cubase, then switch back to Reaper! I don’t think Reaper can reset the sample rate if it was altered by another program… but that may only be true with my particular version of my audio driver!
You could have a conflict with the internal sound device on your computer (disable your internal sound device).
Check your physical connection from external sound card to your computer. (Try a different / proper cable).
Whatever buss format your soundcard uses… (Firewire, USB, PCI, etc. ) check that there is not another device that is sharing that buss, or is hogging the resources from that buss!
Check that there is communication between your hardware and driver outside of Cubase… to rule out a misconfiguation within Cubase!
You appear to have properly set up the driver connections in Cubase outside of the one listed in the first paragraph, so I would concentrate on variables outside of Cubase… Oh! Because you said you could hear your mic when you tap on it… also make sure you don’t have direct monitoring engaged while troubleshooting so you can monitor the signal through Cubase!
I would also check the Tascam forum for your device ( if one exists, or you have not already done so). If your problem is a common one, there will likely be others to help you troubleshoot there!!!