There could be an underlying problem that a vet can determine.
Why Is My Dog Trying To Urinate Without Producing Urine?
The dog could have crystals in its kidneys.
Male dogs cock their legs to mark their territory. When doing this, they only need to pass a drop. So long as he can pee a good quantity when he merely wants to empty his bladder, this is ok.
A female dog repeatedly trying to pee has likely got cystitis - a bladder infection.
A female dog repeatedly trying to pee has likely got cystitis - a bladder infection.