Permalink will now work…

Hi,

I have installed WordPress 4.8 with WooCommerce 3.0.8. I try to set custom permalink. I set the permalink settings to: Common Settings/Custom Structure – Product permalinks/Shop base with category or Common Settings/Custom Structure – Product permalinks/Custom base (/product-category/sample-product). But when I will save it, it comes back to default. I can try to save it as many times I will but still the same result. Each times after save it comes to default.

Please can you help me.