Hi there

You say he ate when you first got him. So he took a few meals with you ?

6 weeks isn't quite crisis mode yet in my opinion.

What is his weight? More importantly then the time frame since he last ate, is his condition. If he isn't losing weight badly i wouldn't stress yet.
My 13 month old pinstripe stopped feeding for six months and only started again last week. She old lost 45 grams in that time.

Assist feeding should be an absolute last resort! Some times they just need a bit of time.

I would skip a feed then try again.