Apology for the inconvenience caused. The issue you're experiencing is due to the recent Joomla v5.2.4 update. We are currently waiting for Joomla's response to confirm whether this is a bug or an intentional syntax change.
In the meantime, a temporary solution is available. Please modify all instances of type="checkbox" in the template’s options.xml file by updating the default attribute. Specifically, if the value is set to default="0", change it to an empty string default="" .
templates/shaper_helixultimate or your_template/options.xml)
For example, change this:
<field name="predefined_header"
type="checkbox"
helixgroup="header"
label="HELIX_ULTIMATE_PREDEFINED_HEADER"
description="HELIX_ULTIMATE_PREDEFINED_HEADER_DESC"
default="0" />
To this:
<field name="predefined_header"
type="checkbox"
helixgroup="header"
label="HELIX_ULTIMATE_PREDEFINED_HEADER"
description="HELIX_ULTIMATE_PREDEFINED_HEADER_DESC"
default="" />
This adjustment should resolve the issue temporarily. We will keep you updated as soon as we receive further clarification from Joomla.
Note: Make sure that your pre-defined header is enabled.

Thank you for your understanding and patience.
Best regards
