The issue is because the items you order volumetric / weight exceed the weight can be handled by the shipping channel.

If you're placing large amount of quantity, try reducing the total number of unit.

This is how the product setting page from a Shopee seller POV.

As you can see, there any few type of shipping channels to choose from. Each of the shipping channel got different maximum weight limit and different area coverage.

For example, if a seller only turn on "Seller's Own Fleet (East Malaysia)" and turn off the rest of the channel, maybe due to they are they are selling bulky item and only wish to fulfill order with their own transportation. And your destination address is within Peninsular Malaysia, then you will be seeing a similar error message as well.

So, it's either due to the total weight exceed the maximum weight allow by the shipping channel or the destination is not within the available's channel's coverage.