sldgt

Hello @p4fbradjohnson ,
Thank You for your reply and for any help.

As you asked this is the list of plugins installed and system info:
Server Environment
Operating System: Linux
Software: Apache
MySQL version: Percona Server (GPL), Release 38.14, Revision 7e0e1cc v5.5.62-38.14
PHP Version: 7.1.11
PHP Max Input Vars: 3000
PHP Max Post Size: 55M

Theme
Name: Sydney Pro
Version: 2.0.15
Author: aThemes
Child Theme: No

Active Plugins
Akismet Anti-Spam – 4.1.3
By Automattic

Black Studio TinyMCE Widget – 2.6.9
By Black Studio

Classic Editor – 1.5
By WordPress Contributors

Contact Form 7 – 5.1.6
By Takayuki Miyoshi

Duplicate Post – 3.2.4
By Enrico Battocchi

Elementor – 2.9.3
By Elementor.com

Envato Elements – 1.1.9 By Envato

Italy Cookie Choices (for EU Cookie Law) – 2.5.2 By Enea Overclokk, Andrea Pernici, Andrea Cardinale

Jetpack by WordPress.com – 8.2.3
By Automattic

Loginizer – 1.4.3
By Raj Kothari

Polylang – 2.6.10
By WP SYNTEX

Polylang Connect for Elementor – 1.0.0
By David Decker – DECKERWEB

Really Simple SSL – 3.2.9
By Rogier Lankhorst, Mark Wolters

Shortcodes Ultimate – 5.7.0
By Vladimir Anokhin

Smart Slider 3 – 3.3.27
By Nextend

Sydney Toolbox – 1.09
By aThemes

TinyMCE Advanced – 5.3.0
By Andrew Ozz

Wordfence Security – 7.4.6
By Wordfence

Yoast SEO – 13.1
By Team Yoast

I have installed other plugins on the site, which are not currently active. This is the minimum number of plugins that I need to keep. I still tried to disable them all except jatpack, elementor, polylang and sydney tool box, but the fatal error has not gone away. At the moment to operate I have to keep your plugin disabled, unfortunately.

Thanks for any help. SL