Boot into Surface UEFI: hold Volume Up, then press Power. When the Surface logo appears, release Volume Up. Once in UEFI, go to Boot Configuration > Advanced Options and look for "Enable Battery Limit" — make sure it's off.
If the toggle is missing, or if turning it off doesn't fix the boot-below-50% behavior → raise this with the seller/refurbisher immediately. A 2-week-old device with this behavior is not acceptable, refurbished or not. You should be pushing for a replacement, not a repair.
Also run a battery report: open Command Prompt as admin and run powercfg /batteryreport. Open the resulting HTML file and check the Design Capacity vs Full Charge Capacity — if Full Charge is significantly below Design Capacity, the battery is genuinely degraded.