Since version 1.7 of Prestashop, the featureCookie SameSitecauses a loss of session on return when POST mode is activated.

2 solutions exist to solve your problem:

Change return mode to GET

To change the return mode :

1. Sign in to your PrestaShop Back Office.
2. Go to the following menu Modules > Module manager.
3. Search for the Scellius module.
4. Click Configure.
5. Click General configuration.
6. Search for the RETURN TO SHOP section.
7. SelectGETin the Return mode parameter.
8. Click Save.

DisableCookie SameSite

If you wish to keep the POST return mode, make the following change:

1. Sign in to your PrestaShop Back Office.
2. Go to the following menu Shop Parameters > General.
3. Set Enable SSL to Yes.
4. Set Enable SSL on the whole website to Yes.
5. Click Save.
6. Go to the following menu Advanced Parameters > Administration.
7. ConfiguringCookie SameSiteto None.
8. Click Save.