Events doe not appear in a list view after upgrade to 3.4.4

Hi I just upgraded from 3.2.21 to 3.4.4 on Joomla 3.4.8. When I view calendar events by month I can see the events listed OK but when I view as a list, ie by year (say) the list is empty. I see the correct number of list items for each month but they are empty, ie like below:

<tr><td class='ev_td_left'>January 2016</td>

<td class='ev_td_right'>

<ul class='ev_ul'>

<li class='ev_td_li' style="border-color:#CCCCFF;">

</li>

<li class='ev_td_li' style="border-color:#FF6666;">

</li>

<li class='ev_td_li' style="border-color:#33CCFF;">

</li>

And when I click on an event from a month view it is empty, ie no details, title or event date etc.

Support details:

PHP Version : 5.6.15

MySQL Version : 5.5.5-10.1.9-MariaDB

Server Information : Windows NT SWIFT-PC 6.2 build 9200 (Windows 8 Home Premium Edition) i586

Fix jQuery? : Yes

Load JEvents Bootstrap CSS? : No

Max Input Vars ? : 2000

Club code set? : No  

User Agent : Mozilla/5.0 (Windows NT 10.0; WOW64; Trident/7.0; rv:11.0) like Gecko  

Joomla : 3.4.8

component_com_jevents : 3.4.4

component_com_jce : 2.5.14

module_mod_jevents_cal : 3.4.4

module_mod_jevents_custom : 3.4.4

module_mod_jevents_filter : 3.4.4

module_mod_jevents_latest : 3.4.4

module_mod_jevents_legend : 3.4.4

module_mod_jevents_switchview : 3.4.4

plugin_content_jevents : 3.4.4

plugin_finder_jevents : 3.4.4 (not enabled)

plugin_search_eventsearch : 3.4.4 (not enabled)

plugin_system_gwejson : 3.4.4

I have switched on Joomla debug and maximum debug level. I cannot see obvious errors in the sql. Is there a data migration exercise or other step needed in this upgrade?

Many thanks in advance for any assistance.