AMP Issue, CSS syntax error “style amp-custom”

Hello guys,

The Google Search Console raised me an error on ALL my AMP pages.
This is a CSS syntax error in the tag “style amp-custom”.

The code highlighted in the search console is the following (and seems to be linked to Mailpoet) :

<![CDATA[.mailpoet_hp_email_label{display:none}#mailpoet_form_1 .mailpoet_paragraph{display:inline-block;width:45%}#mailpoet_form_1 .mailpoet_text_label/*AMP_WP_BETWEEN_SELECTORS*/,#mailpoet_form_1 .mailpoet_textarea_label/*AMP_WP_BETWEEN_SELECTORS*/,#mailpoet_form_1 .mailpoet_select_label/*AMP_WP_BETWEEN_SELECTORS*/,#mailpoet_form_1 .mailpoet_radio_label/*AMP_WP_BETWEEN_SELECTORS*/,#mailpoet_form_1 .mailpoet_checkbox_label/*AMP_WP_BETWEEN_SELECTORS*/,#mailpoet_form_1 .mailpoet_list_label/*AMP_WP_BETWEEN_SELECTORS*/,#mailpoet_form_1 .mailpoet_date_label{display:block}#mailpoet_form_1 .mailpoet_text/*AMP_WP_BETWEEN_SELECTORS*/,#mailpoet_form_1 .mailpoet_textarea/*AMP_WP_BETWEEN_SELECTORS*/,#mailpoet_form_1 .mailpoet_select/*AMP_WP_BETWEEN_SELECTORS*/,#mailpoet_form_1 .mailpoet_date{display:block}#mailpoet_form_1 .mailpoet_validate_success{color:#468847}#mailpoet_form_1 .mailpoet_validate_error{color:#b94a48}#mailpoet_form_1 .mailpoet_submit{background-color:#a3a375;color:#fff}:root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-7865d8c{font-family:moon-flower-bold;font-size:36pt}:root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-7d27179{text-align:justify}:root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-d994343{max-width:500px}:root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-93b8ea5{display:none}:root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-e6a44be{display:inline-block}:root:not(#_):not(#_):not(#_):not(#_):not(#_) .amp-wp-2f58115{width:0%} </style>

And when I go in my AMP plugin settings, I have an error message saying : “A conflicting version of PHP-CSS-Parser appears to be installed by another plugin/theme (located in ‘plugins/mailpoet’). Because of this CSS processing will be limited, and tree shaking will not be available.”

So it seems there is a conflict between AMP and Mailpoet but I have no idea what to do to solve it.
Could you guys tell me if this is something to fix on your side ? Or should I do something (and what if it’s the case) ?

Thanks in advance

The page I need help with: [log in to see the link]