I started getting these errors after I changed theme base(advanced settings) from existing theme to Sunburst after I migrated my site to Plone 5.0.6

Plone Support Theming
1

2017-04-26T06:42:39 INFO ZEO.ClientStorage zeostorage Server authentication protocol None

2017-04-26T06:42:39 INFO ZEO.ClientStorage zeostorage Connected to storage: ('staging', 8100)

2017-04-26T06:42:39 INFO ZEO.ClientStorage zeostorage No verification necessary (cache_tid up-to-date '\x03\xbe\xe0w\xd6t\xce\x00')

2017-04-26T06:43:11 ERROR root Exception while rendering an error message
Traceback (most recent call last):
File "/usr/local/plone-5.0/buildout-cache/eggs/Zope2-2.13.24-py2.7.egg/OFS/SimpleItem.py", line 240, in raise_standardErrorMessage
v = s(client, REQUEST, **kwargs)
File "/usr/local/plone-5.0/buildout-cache/eggs/Zope2-2.13.24-py2.7.egg/OFS/DTMLMethod.py", line 146, in call
r = apply(HTML.call, (self, client, REQUEST), kw)
File "/usr/local/plone-5.0/buildout-cache/eggs/DocumentTemplate-2.13.2-py2.7-linux-x86_64.egg/DocumentTemplate/DT_String.py", line 477, in call
try: result = render_blocks(self._v_blocks, md)
File "/usr/local/plone-5.0/buildout-cache/eggs/Zope2-2.13.24-py2.7.egg/OFS/DTMLMethod.py", line 137, in call
r = apply(HTML.call, (self, client, REQUEST), kw)
File "/usr/local/plone-5.0/buildout-cache/eggs/DocumentTemplate-2.13.2-py2.7-linux-x86_64.egg/DocumentTemplate/DT_String.py", line 477, in call
try: result = render_blocks(self._v_blocks, md)
Unauthorized: You are not allowed to access 'title_or_id' in this context

2017-04-26T06:43:11 INFO plone.app.theming.policy local cache invalidated on thread 139718440253184

2017-04-26T06:43:11 INFO plone.app.theming.policy initializing local cache on thread 139718440253184 for http://xx.xxx.xxx.xxx::barceloneta

I started getting these errors after I changed theme base(advanced settings) from existing theme to Sunburst after I migrated my site to Plone 5.0.6

2

dont do that.
Sunburst will not work in Plone 5, and theme base should very rarely be changed.

3

Since we are unable to login to the server and getting permission errors then how do I revert back the changes.

4

try to go to http://yourzopeserver/manage_main and click the UNDO tab

5

Visiting this link gives me 404 error

6

replace "yourzopeserver" in the url with the actual one of your site.

7

Were you able to undo?

If not, go to your site's Site Setup, click on "Management Interface", then click the Undo tab.