I am on 5.6 i wana buy assest from 5.6.1 why i am not allowed to do this.
Speak with asset creator. It is very possible he have later version or he can create pack using later Unity version.
Buy it from the website (https://www.assetstore.unity3d.com), not inside the Unity editor. Or install Unity 5.6.1 in a separate location and buy it from there. You’ll still need to install Unity 5.6.1 to download the asset. Then you can try to import it from your download cache into your Unity 5.6 project. The asset creator may not be able to support you, though, since the asset was published for 5.6.1 and higher.
well i am trying to avoid downloading 5.6.1
So looks like no way since even if i buy it from assest website i would still need 5.6.1 to download it
Unless, as mr_Necturus wrote, you can convince the asset creator to submit a new version with Unity 5.6 or earlier.
For purchasing through Unity editor try this:
Add the asset to your wishlist.
Show your wishlist.
Click on the small shopping cart icon beside your desired asset.
Proceed with checkout.
From my experience this way prevents the version check.
You still can’t download the asset though. But its in your inventory. Especially handy for sales.
I also don’t understand the artifical restriction UT puts on our backs here. A short warning that you can’t use it with the current Unity version would suffice from my POV.