。
I hope I can be of help on another occasion.
Literal
Different opportunity [at-に] useful become-can [thing-こと] [object-を] hoping am.
お役に立てる is the potential of 役に立つ ('to be useful') with the polite お prefix — 'to be able to be of service.' ことを願っています is 'I am hoping that.' This is formal business-letter language expressing willingness to help in the future.