Tatyana,
from your screenshot I see that you created a custom service product Z_INVESTIGATION.
What was the reason for that ?
Are you using standard SLA Management for Incidents or you have special case (like for example SLA by multi-level categorization) ?
I am asking because for standard SLA you do NOT need to create a copy of INVESTIGATION.
And in this case you can just try to update the standard INVESTIGATION product with your service and response profiles.
according to this blog SLA Management - SAP IT Service Management on SAP Solution Manager - SCN Wiki in paragraph 3.3.1 you see that INVESTIGATION is hardcoded in the system and if it cannot identify your custom setting - it will always fall back to use standard INVESTIGATION product, which by default works exactly as you described (3 days and no exceptions) - and I think this is what is happening in your case.
I have configured my SLA to work based on Multi-level categorization, in my case I had to create a copy of INVESTIGATION product because I needed to have different response profile for each category, but then I had to specify my custom service product in the Categorization definition. It works for me and calculates everything correctly.
So it depends on how you want to use it. But generally the standard INVESTIGATION product is just fine for simple cases. Please try to use it first.
Oh, and one more thing in the screen you shown, please check the tab "Service" for your product and make sure in "Transaction Control Fields" the field "Item Cat. Group" shows SRVP.
It was missing in my case and was causing issues.
Regards
Elena