Problem with Catproduct

[milos_pa]

Hi,
I have a website that uses Catproduct. It is working fine for 3 years, and now is time to upgrade php to 7.3...and Catproduct works on 5.6.
There is no support from SM-Planet (developers), no email answered, no skype...nothing!!!
I made an dev site (clone of working version). Updated Joomla 3.9.21 , updated VM 3.8.4 and php to 7.3.
Idea is to try to rewrite Catproduct .
Problem is that I get an error "ANNOT ACCESS PROPERTY STARTED WITH '\0'", but there is nothing in any log files, nor console, nor networking. Errors are set to "developer", vmdebug is on...but notihng in error logs to start with...
link to the product page is: https://sifonjer.top/elementi/perece

Does anyone know how to turn on errors or even better is there a solution for Catproduct?
Grateful in advance,
Milos

[pinochico]

We use on PHP7.3.2

www.kolo-park.cz - catproduct
www.svicky.biz - catproduct, catproduct content

Custom develop for PHP 7.3 - fix errors inside plugin for content and JS for catproduct.

Maja from catproduct is not reflected on email or skype two years, our subscription ended on 2019

[pinochico]

Why do you use old gavick template for J25?

# StoreFront - April Joomla! template (for Joomla 2.5)
#
# Copyright (C) 2007-2014 Gavick.com. All Rights Reserved.

Gavick now is under Joomlart and all template are updated...
I don't understand