Dissolve Silver Nitrate Difficulty...

Hello a friend has had difficulty with dissolving Silver Nitrate, is this a common issue or something which can be remedied with temperature or regrinding to a fine powder?
Thanks for any response.

This issue has been resolved the AgNO3 was not what it was thought to be as a student in the shop supplying this gave the wrong crystal...
I had asked the question if they were sure it was Silver Nitrate. Ha Ha!