Victor, the Eureka RD belts will NOT work on a Hoover Convertible. The Hoover belt is a little tighter fitting than the Eureka belts are - that's why some people will save worn out Hoover Convertible belts to use on their Eureka uprights. As for other causes of belt slippage, I would also check to see if the belt pulley is worn out & due for replacement.
For your new to you convertible is the 44783. They replaced the obsolete 49258 and are designed for the commercial Guardsman machines, which are based on the OG Convertible. They are softer and last forever! I've had the same ones on my convertibles for over a year with no signs of slowing down
And, the bag matched , too. That is a replacement (but genuine) bag.
I fin great Hoover belts in the sealed package,,, usually with the orange Ranger vacuum on the package. Tom Anderson taught me a little trick with belts.
I replaced it with an Old, unused RD Belt I had lying around and it worked!. It took a lot or some stretching, but it works. It doesn;'t slip and it grooms my carpets perfectly. The Old belt was very chewed up and had soemthing looking like the start of new tears. It also kept slipping and left black marks in my carpet which I may be able to rmove with my Cleanslate.