Event editor can't see calendar

We have a single calendar on our website with viewing access set to Public. We also have a few usergroups (UG) defined with permissions to post/edit calendar events. We've recently begun encounting a problem. On the front end, the calendar is visible but if a user of one of the UGs with edit/post permissions logs in, the calendar is no longer visible - either a blank page appears or a "No Calendar Events Found or Calendar not set to Public." is displayed. When they log out, the calendar is agin visible.
We've not changed any permissions or access levels in JEvents. We did update Joomla to 3.8.8 but can't say definitively if the problem coincided with the update.

This is the info dump from JEvents Support Info:

PHP Version : 5.6.36

MySQL Version : 5.5.5-10.1.33-MariaDB

Server Information : Linux us-wpl-c3-ss146.wpl.host 3.10.0-693.17.1.el7.x86_64 #1 SMP Thu Jan 25 20:13:58 UTC 2018 x86_64

Fix jQuery? : Yes

Load JEvents Bootstrap CSS? : Yes

Max Input Vars ? : 1000

Club code set? : No  

User Agent : Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:60.0) Gecko/20100101 Firefox/60.0  

Joomla : 3.8.8

component_com_jevents : 3.4.46

component_com_jce : 2.6.8

component_com_hikashop : 3.4.0

module_mod_jevents_cal : 3.4.46

module_mod_jevents_custom : 3.4.46

module_mod_jevents_filter : 3.4.46

module_mod_jevents_latest : 3.4.46

module_mod_jevents_legend : 3.4.46

module_mod_jevents_switchview : 3.4.46

plugin_content_jevents : 3.4.46

plugin_finder_jevents : 3.4.46 (not enabled)

plugin_installer_jeventsinstaller : 3.4.46 (not enabled)

plugin_search_eventsearch : 3.4.46

plugin_system_gwejson : 3.4.46

At the top of the page is also this warning message:"234 - Your php setting for max_input_vars may be too low (currently it is 1000) - if you have problems updating your configuration options then please ask your webhost to update this setting to 2000." Could this be the cause of the problem?