проверьте

[FIrina]

Проверьте, пожалуйста:

Если при размещении рекламных материалов Заказчика, осуществляемых исходя из утвержденного Сторонами объема, услуги были оказаны не в срок и/или в ненадлежащем объеме, Исполнитель обязуется в согласованные с Заказчиком

Мой вариант:

In case if Contractor fails to place the advertising materials in due time and/or render services in a volume approved by the Parties, the Contractor is obliged to perform services in the volume of unperformed in time agreed with the Client.

[_03]

consider:
If Contractor fails in its performance of advertising placement [work] to meet either the time limits or the scope of work as agreed on between the Parties the Contractor shall

[FIrina]

Спасибо!!!

[tumanov]

should Contractor fail to render the service of placing Clients's advertising materials in full and/or in due time as agreed, the Contractor shall ...

но по-моему тут еще попроще надо, подрезав русский язык
:
should Contractor fail to place advertising materials of the Client in full and/or in due time as agreed, the Contractor shall ...