Page Error

We have only recently launched our website last few days and gradually starting to get members signing up (current membership is only 5 - excluding myself)

A new member signed up yesteday and tried adding an event but on submitting the form she got "Page Not Found" error message and she tried again with similar result.

However, both attempts created a public feed timeline post "...added an event" each time and also updated the public events calendar each time.

On clicking the posts from the public feeds timeline there is a Page Not Found error. Similar error message is encountered on clicking them through the public calendar listings. 

The created events are also not showing in the new events page either.

I have been trying the best part of last night and this morning to figure out what had gone wrong as I had previously successfully created a test event few days back before starting to invite members but still cannot resolve the issue.

In an attempt to work out what might be going on and to check if it is just the Events module that is playing up I tried creating a group (as Admin) and had similar issues.

On submitting the creation of the group form I got a page error message and a second attempt came up with similar result...the public post feed timeline is similarly showing them as being added and clicking on the public feed post for each of them gives same page error message.

(I did quick creations on Polls and Discussions modules also to check and they are working as expected)

Any assistance on resolving this would be greatly appreciated as I have got some new members lined up to join and the Events and Groups are key functions they will be using, thanks.

[NB. We are on a Cloud4 plan so do not have access to the backend]