I'm trying to upload the folders and files for the Simple:Press core plugin. It's an upgrade and I have already deleted the old folders and files. When uploading the new files, i'm getting the message 'Critical File Transfer Error" and my error log shows many messages including the following:

PHP Warning: Creating default object from empty value in /content/sites2/c/o/communityhub.ie/web/wp-content/plugins/simple-forum/library/sf-database.php on line 2094
PHP Warning: Creating default object from empty value in /content/sites2/c/o/communityhub.ie/web/wp-content/plugins/simple-forum/library/sf-database.php on line 2094
PHP Warning: Creating default object from empty value in /content/sites2/c/o/communityhub.ie/web/wp-content/plugins/simple-forum/library/sf-database.php on line 2094
PHP Warning: Creating default object from empty value in /content/sites2/c/o/communityhub.ie/web/wp-content/plugins/simple-forum/library/sf-database.php on line 2094
PHP Warning: Creating default object from empty value in /content/sites2/c/o/communityhub.ie/web/wp-content/plugins/simple-forum/library/sf-database.php on line 2094
PHP Warning: Creating default object from empty value in /content/sites2/c/o/communityhub.ie/web/wp-content/plugins/simple-forum/library/sf-database.php on line 2094
PHP Warning: Creating default object from empty value in /content/sites2/c/o/communityhub.ie/web/wp-content/plugins/simple-forum/library/sf-database.php on line 2094
PHP Warning: Creating default object from empty value in /content/sites2/c/o/communityhub.ie/web/wp-content/plugins/simple-forum/library/sf-database.php on line 2094
PHP Warning: Creating default object from empty value in /content/sites2/c/o/communityhub.ie/web/wp-content/plugins/simple-forum/library/sf-database.php on line 2094
PHP Warning: Creating default object from empty value in /content/sites2/c/o/communityhub.ie/web/wp-content/plugins/simple-forum/library/sf-database.php on line 2094
PHP Warning: Creating default object from empty value in /content/sites2/c/o/communityhub.ie/web/wp-content/plugins/simple-forum/library/sf-database.php on line 2094
PHP Warning: Creating default object from empty value in /content/sites2/c/o/communityhub.ie/web/wp-content/plugins/simple-forum/library/sf-database.php on line 2094
PHP Warning: Creating default object from empty value in /content/sites2/c/o/communityhub.ie/web/wp-content/plugins/simple-forum/library/sf-database.php on line 2094
PHP Warning: Creating default object from empty value in /content/sites2/c/o/communityhub.ie/web/wp-content/plugins/simple-forum/library/sf-database.php on line 2094
PHP Warning: Creating default object from empty value in /content/sites2/c/o/communityhub.ie/web/wp-content/plugins/simple-forum/library/sf-database.php on line 2213

Any idea why I can't upload? Thanks in advance for your help.

can you explain what you are doing??  this looks like a very, very old version of simple press 4.x... its not even supported any more...  and those are just warnings...

with version 5, simple press goes in wp-content/plugins/simple-press...  your warnings are referencing the old data structure (ie simple-forum)...  you cannot have a version 4.x and version 5.x on the same install... 

Thanks for your reply, Mr Papa. I'm trying to upgrade from 4.5.1 to the latest version. I'm following instructions here exactly http://codex.simple-press.com/.....rsion-4-5/ and I understand that the Simple:Forum files need to remain installed so that I don't lose the topics and posts already created. My hosting company have since given me the required permissions to create a new directory (Simple-Press) in order to upload the new files. 

Having read your message above, i'm getting worried about having the Simple-Forum directory there, because I will have version 4.5.1 and v5 in the same install, isn't that correct? There are no instructions to remove the Simple:Forum files once the Simple:Press install is done.

Sorry but please re-read the very first paragraph of that Codex article. You need to completely remove ALL of the plugin files and remove the old folder. Ad it says - deactivate and remove. Do NOT uninstall as that will lose data.

Just follow the step by step instructions,

Thanks but I find this confusing because in the WP Admin, the name of the plugin was listed as Simple:Press v4.5.1. I clicked 'deactivate' and then 'delete' (as per Step 2) and now it is gone from the WP Admin Plugins list. This is how I understood from Step 2 to delete the plugin folders and files. However, when I try to upload the new files via Filezilla (Step 3), there is a directory called 'Simple-Forum' in the Plugins folder which does not show in the WP admin plugins list. Actually, the folder contains no files, so will I just delete it?

Also, i'm not sure what you mean by not 'uninstalling' - is that not the same as removing folders and files? Thanks in advance.

Yes- as I saod above - remove the old folder.

And - as the article states - the folder is no longer called 'simple-forum' it is now called 'simple-press'.

Uninstall is an optipn you can set within Simple:Press to remove all data upon deactivation. That would remove all of your forums, topics, posts etc.

By the way - if you can avoid using FIleZilla I would. It has been known to cause many problems in the past.

Sorry - meant to add that the name of the plugin has been 'simple:press' for a long time. But the folder up until V5.0 was not the same. And that is why we took the opportunity of changing it.

Thank you, all upgraded now 

Excellent. Glad to hear it.