I noted when I click to download the 5.2.6 version, as zip file named sendy-126.96.36.199.zip. Is this the correct file?
If you download Sendy and you get the version 188.8.131.52 zip, it's because your license key is a 4.x license key.
Upgrade your license key to 5.x at https://sendy.co/get-updated. After which you will be able to download the latest version in the 5.x series.
Perfect. Thank you!