Quality is delighting customers
Below are some of the challenges which are commonly encountered/faced by many software testing providers during different phases of testing:
1. Improper communication workflow(Like: Time lines are not clearly defined and communicated within all the teams, No proper followups/feedback providing process, Not escalating right issue to the right authorized person etc)
2. Non availability of resources(Like:Stable testing environment,Hardware/software resources etc)
3. Product estimates not close to reality(Like: Not properly calculated, Unrealistic assumptions/expectations etc)
4. Not analyzing,Implementing and following right approach/model for the product(say. agile)
5. Dev not running parallel with QA to meet the defined test timeline.
6. Testing /development scopes(In-Scope/Out of Scope areas/features) not identified/defined prior to starting of testing.
So in order to deliver quality product to client one need to take care of the above points which is already been taken care by many software testing solutions at an initial level itself so that such challenges are no longer an obstacle.
I hope my answer helped.