path.split не является функцией react chrok form
react-hook-form updated to 7.0.0 from 6.X.X and has breaking changes:
You have to replace all ref={register} with {...register('value_name')}
Version 6.X.X:
<input ref={register({ required: true })} name="test" />
Version 7.0.X:
<input {...register('test', { required: true })} />
raadu