As a sales leader within your startup you should take responsibility for the failures and share the credit for your wins.
When you are not successful, you, as a startup founder are best placed to make corrective changes.
You should have the best understanding of your startup. Employees are not as well positioned to know what changes need to occur.
Even if the person hired has failed, you should also take responsibility as you hired them, and/or neglected to train them properly.
In management 101, you should always assume that most employee problems are a result of the environment they work under. Take responsibility for when things don’t go to plan.
On the flip side giving credit to all involved when you achieve a win is a unifying activity. I once worked for a CEO founder who tried to claim credit for the sales he had helped me with. This was a poor move for him and his company.
Be the better man or woman!