Ah yes, thanks, @jan, I see that all of the tags within in my local config_viewer.xml
had double /viewer/viewer
in their paths - entirely my fault of course 
I ran the a2enmod as you suggested, and then tried to load the url…
This is where /var/log/tomcat**8**/catalina.out
starts reporting the problem:
18-Nov-2020 07:09:03.149 SEVERE [ajp-nio-127.0.0.1-8009-exec-10] com.sun.faces.application.view.FaceletViewHandlingStrategy.handleRenderException Error Rendering View[/viewObject.xhtml]
javax.el.ELException: /file:WEB-INF/lib/viewer-core-4.12.0.jar!/META-INF/resources/resources/components/widgets/widget_views.xhtml @136,110 rendered=“#{cmsBean.isHasRelatedPages(activeDocumentBean.viewManager.pi)}”: javax.persistence.PersistenceException: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.7.7.v20200504-69f2c2b80d): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: java.sql.SQLSyntaxErrorException: (conn=88) Table ‘viewer.cms_pages’ doesn’t exist
Error Code: 1146
Call: SELECT cms_page_id, date_created, date_updated, may_contain_url_parameters, page_sorting, parent_page, persistent_url, published, related_pi, static_page, subtheme_discriminator, template_id, use_default_sidebar, wrapper_element_class FROM cms_pages WHERE (related_pi = ?)
bind => [1 parameter bound]
Query: ReadAllQuery(referenceClass=CMSPage sql=“SELECT cms_page_id, date_created, date_updated, may_contain_url_parameters, page_sorting, parent_page, persistent_url, published, related_pi, static_page, subtheme_discriminator, template_id, use_default_sidebar, wrapper_element_class FROM cms_pages WHERE (related_pi = ?)”)
And this is /opt/digiverso/logs/viewer.log
:
DEBUG 2020-11-18 07:15:02.188 [ajp-nio-127.0.0.1-8009-exec-2] io.goobi.viewer.managedbeans.ActiveDocumentBean.update(ActiveDocumentBean.java:300)
update(): (IDDOC 1605625199167 ; page 1 ; thread 132)
ERROR 2020-11-18 07:15:02.378 [ajp-nio-127.0.0.1-8009-exec-2] io.goobi.viewer.exceptions.MyExceptionHandler.handle(MyExceptionHandler.java:85)
CLASS: javax.el.ELException
ERROR 2020-11-18 07:15:02.378 [ajp-nio-127.0.0.1-8009-exec-2] io.goobi.viewer.exceptions.MyExceptionHandler.handle(MyExceptionHandler.java:262)
/file:WEB-INF/lib/viewer-core-4.12.0.jar!/META-INF/resources/resources/components/widgets/widget_views.xhtml @136,110 rendered=“#{cmsBean.isHasRelatedPages(activeDocumentBean.viewManager.pi)}”: javax.persistence.PersistenceException: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.7.7.v20200504-69f2c2b80d): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: java.sql.SQLSyntaxErrorException: (conn=88) Table ‘viewer.cms_pages’ doesn’t exist
Error Code: 1146
Call: SELECT cms_page_id, date_created, date_updated, may_contain_url_parameters, page_sorting, parent_page, persistent_url, published, related_pi, static_page, subtheme_discriminator, template_id, use_default_sidebar, wrapper_element_class FROM cms_pages WHERE (related_pi = ?)
bind => [1 parameter bound]
Query: ReadAllQuery(referenceClass=CMSPage sql=“SELECT cms_page_id, date_created, date_updated, may_contain_url_parameters, page_sorting, parent_page, persistent_url, published, related_pi, static_page, subtheme_discriminator, template_id, use_default_sidebar, wrapper_element_class FROM cms_pages WHERE (related_pi = ?)”)
javax.el.ELException: /file:WEB-INF/lib/viewer-core-4.12.0.jar!/META-INF/resources/resources/components/widgets/widget_views.xhtml @136,110 rendered=“#{cmsBean.isHasRelatedPages(activeDocumentBean.viewManager.pi)}”: javax.persistence.PersistenceException: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.7.7.v20200504-69f2c2b80d): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: java.sql.SQLSyntaxErrorException: (conn=88) Table ‘viewer.cms_pages’ doesn’t exist
Error Code: 1146
All the best,
Stephen