I'll first ask myself why someone would reject your commission proposal, usually, fake/incomplete/recently made accounts are most likely to be rejected by artists, since it could be considered a scam. But leaving that aside, I wonder how you're approaching these artists that they leave you "on read" because at least on my case, I do answer even if I have commissions closed or the type of commission is not within my services.
Regarding where to find one, you can always open up a thread in the Collaboration category in this Forum, detail what's the type of work you're looking for, be the type of art (Cover, Illustration, Character Sheet), it's style (cartoon, anime, semi-realistic, or you can just put samples of what you're looking for), approximate budget and payment method.
As well, you can make a Tweet on Twitter App and using the hashtags "LookingToCommission" "DigitalArt" or similar, to be seen and usually, artists offer their samples in replies.
You can search on Commission Groups on Facebook, there is always people posting their prices and samples there, or you can make a post and then artists will comment and Dm you.