Multidomain setup works with unsecure links, but not with secure links

[DrCashew]

I have one Magento website, with 6 different stores and 1 storeview per store. They have one codebase. The different domainnames are setup with domainpointers to the main-domain (domain1.nl).

They all have different domainnames, except one, which is a subdomain of one of the stores, like this:

• domain1.nl (secure // HTTPS)
• subdomain.domain1.nl (unsecure // HTTP)
• domain2.nl (unsecure // HTTP)
• domain3.nl (unsecure // HTTP)
• domain4.nl (unsecure // HTTP)
• domain5.nl (unsecure // HTTP)

The above setup works. But if I want to set all domains with SSL (Let's Encrypt - one certificate), the websites work, but the session is not passed to the other stores. Resulting in logged out users and empty carts.

I am using Magento 1.9.2.4

Does anyone know what I am doing wrong? Thanks in advance.

[kab8609]

It is based on the domain name in the cookie. So it gets sets with one domain name, then when you go to another the domain name isn't the same anymore so you have to log in again.