Brand new summerhouse leaking like a sieve - I'm assuming it shouldn't be??

I have just had a summerhouse installed (2 weeks ago, put up by the company I bought it from.) I haven't been in it much given the weather but popped out yesterday to find that it not remotely rain proof. One side panel is soaked top to bottom. Another panel has rivulets running down it. Other panels have large damp patches. And there are a number of small but annoying puddles collecting around the edge of the shed, where wall panels meet the floor. My question is, how water tight can I reasonably expect a wooden summer house to be? I'm pretty miffed at the moment but it does come with a decent guarantee so I'm reasonably sure the company will do something...but I am never the less worried about the integrity of the structure. Im not sure what to ask them to do about it. Any advice or thoughts would be really helpful. (It is 6 foot x 8 foot and cost £800 ie not top of the range but not the cheapest either.)

It should be water tight. Has the wood shrunk as it's dried out a little?

I built a large shed this summer with shiplap t&g and from day 1 it's been bone dry.

Are there are any visible gaps in yours?

Not really any visible gaps. Should it have dried out that much in 2 weeks?

Should be watertight assuming the area it stands in does not get standing water to leech into the floor.