Vendor autoload is not found. Please run 'composer install' under application root directory.

[bilal_baydoun1]

I installed composer using SSH on my cloud Hostgator hosting 

Composer version 1.6.5 2018-05-04 11:44:59 

 but I'm still getting this error when I go for setup:

Autoload error

Vendor autoload is not found. Please run 'composer install' under application root directory.

Any idea what's going on?

Thanks

[Manthan Dave · Accepted solution]

Hi @bilal_baydoun1

have you installed composer ?

do one thing run command from - composer install from your root directory of magento 2

then check it will works , 

Make sure you run command in magento 2 root directory

[philip_denys]

no doesn't work for me :/

I get this alert:

 - Installing vertex/sdk (1.0.0): Downloading (100%)

  [UnexpectedValueException]
  The checksum verification of the file failed (downloaded from https://repo.magento.com/archives/vertex/sdk/vertex-sdk-1.0.0.0.zip)