This is a recent update conflict. If you didn't ever create a recovery USB you will have to download the recovery image , put it on a USB, boot to it and refresh the RT.
https://www.microsoft.com/surface/en-us/support/warranty-service-and-recovery/downloadablerecoveryimage
Copy the contents of the unzipped file to a fat32 formatted USB, turn the RT off, hold the volume down button and start the RT with the start button, release the volume down button when the surface logo appears. I t will take a while to boot from the USB, wait.
You have to install updates again.
The conflict is from KB3033055 and
2018-01 Security Monthly Quality Rollup for Windows RT 8.1 for ARM based systems KB4056895
You can not install KB3033055 if KB4056895 has been installed. Do your updating from the control panel, windows update, and hide KB4056895,
KB3033055 is the one that gives the Win 10 interface and shows up in optional updates. Both will show up at the end of all other updates
See my post, control RT Updates and 'Check for updates but let me choose whether to download and install them'
https://forums.windowscentral.com/microsoft-surface-windows-rt/