Hi and welcome to the site, I’m Louie. Sorry you had to wait awhile but I’ll do my best to help.
Initially, error display "E1" would indicate an internal hardware issue or more particularly, the speed sensor is not able to detect (correct) motor speed. It may be as simple as a loose/dislodged speed sensor and/or its connector/wire, dirt/dust/obstruction between the speed sensor and motor pulley or controller failure. Any of these would require that the unit be opened up to effect repairs.
Are you then considering a DIY (do-it-yourself) repair approach? If yes, do you have access to and familiar with a multi-meter