You applied for a Schengen on very short notice and by the time they reached a decision, the premise for your visit was no longer valid. If your application was still in the pipeline when the meeting took place (1 July - 7 July), then it didn't make sense for them to issue the visa.
When these situations arise, the application enters a state they call "incoherence". When an application is 'incoherent' they use checkbox 2: "Justification for the purpose and conditions of the intended stay was not provided".
Do you think i've got refused because of intervention between
interview date and visit date ?
Yes, that's what the indications are based upon the information you have provided.
And what am i suppose to do now especially we have another office
meeting at Sep-15
A different meeting on different dates is a different premise. You will need to make a fresh application.
do i have to appeal with the new ticket and accommodation date 15-30 SEP
or i have to reapply one more time
There is no case for them to answer. Dates are as mechanical as you can get.
They were correct to refuse and an appeal will get you nowhere. Your most expedient remedy is to make a fresh application from square 1. They have the option, but not the obligation, to get fresh biometrics from you next time so you might not need to take that step.
i don't got any stamp on my passport
And? You will need to declare your previous refusal.
Note: as pointed out by colleague Michael Hamilton (to whom thanks), your question bears a lot of similarity to an existing article here. Schengen Visa Refusal: Justification for the purpose and conditions of the intended stay was not provided You are emphatically advised to read it carefully.