Infinite bucle HTTPS/HTTP - How to kill old cookies

[kartdepedales]

We have a serious issue with one of our clients. They have been using SSL certificate for the entire website. However during the last month they have migrated their website to one of our servers. During this process they decided to use HTTP instead of HTTPS due to some security error messages in some devices.
 

The problem is when someone access to the website via https://antihumedades.es save a cookie in his computer and he can no longer access to the normal website: http://antihumedades.es

And the problem is happening also when somebody has cookies from the former version (https)

 

Is there any way to "kill" the old cookies in prestashop?

I've found an old topic about a module but that module never exists.

 

Thanks in advance