Hi,
I suppose that you're talking about the display of the MSRP on the products listings on your website, since for some products I can see the MSRP on the product details page, but not on the listing.
However, there is no option in HikaShop to display the MSRP on the listings.
So I suppose that you've made a modification to the product / listing_price.php view file to display the MSRP on the listings.
So first, it could be linked to the way you did your customization.
And second, you need to know that the display of the listing_price.php will only happen if the "display price" setting of the current menu item is activated. So what's probably happening is that you configured one menu item for each category, and for some of the menu items, you have that "display price" setting turned off.