If it just barely doesn’t fit, a little bit of super glue/silicone should keep it on and keep water out. It’s main function is to protect the inner lock ring I believe from the elements

Sounds like your bottom bracket is longe than 73mm

my bottom bracket is 94mm

i have ordered this adapter to fit my bafang bbs01 unit hopefully it is what you need

https://caprouge.com.au/collections/chain-wheels/products/lekkie-bb86-92-bafang-adapter