Looks to me the guy has written on that note "Any problems Please don't hesitate to ask"?
Did you call him or did he explain on which direction to twist to tighten the string?
Assuming like many I hold the bottom loop and twist counter clockwise for a right hand bow ...
The guy could of made some instruction copy's on paper on how to twist his strings ...
I never sell mine but had made well over a few hundred if not more and if I don't know the person I always explain which direction to twist ,strand count and what bow it was intended for if I knew of coarse....
By the guys note it seemed he was willing to solve a problem "But" if it were me I would of just made you another to keep a happy customer...
Have you been shooting traditional bows long and do you know the difference's in a Flemish twist verses a Continous loop string?
A flemish twist can come apart by the customer as well if not twisted properly when bracing the bow....
Mike Mecredy Stepped forward and said He will fix it and that just shows that many here as Trad shooters are great people ...
If you ever need another remember to come here and ask for a reliable stringmaker and there are several great makers here...If you are looking for a very cheap one for $10.00 including shipping more then likely it too may come apart ...
On average for a B-50 most are getting $16.00/$18.00 for one and that's worth every penny cause it takes me a good 1/2 hour to do one right including the serving and sometimes an hour... The fast flight is around $20.00 to $22.00 or more but just price the materials and time to make it and include the shipping charge's...
The guys do it mostly for just a few bucks really...
My personal opinion is the fella didn't taper or give it much back twist leaving the loops...