Boot back to TWRP. Wipe Cache/Dalvik. If that fails, perform a "Factory Reset" (which wipes data but not internal storage). If still looping, you flashed the wrong ROM variant (T585 vs T580).
Flashing custom software carries risks including voiding your warranty (if any remains), tripping Knox, and potentially bricking your device. You assume full responsibility. This guide is for the SM-T580 only – not the T585 (LTE) or T581. sm t580 xda
Your Windows PC needs to recognize the tablet. Download the latest Samsung USB drivers from the XDA thread or Samsung's official site. Boot back to TWRP
Reading through the forums reveals common user errors. Avoid these: sm t580 xda