It’s hard to say just not knowing your install and set up really. But, BuddyPress does work without Multisite so if you are having issues my advice probably in this case would be to export the contents you want and put on a fresh site.
However, others may have something better as this is a bit of a brutal fix. It’s just that so many things could be at play I’m always keen to strip back as much as can.
If you do not want the users blog content then you can export the BP database and re install it on a fresh site. The users blog content can be export by each user and then they can do what they want with it.
these plugins may help:
https://wordpress.org/extend/plugins/navayan-csv-export
https://wordpress.org/extend/plugins/bp-export-users
Have you started by doing all the basic steps:
1. Make a copy of your site (so you are not working on the live server)
2. Deactivate all plugins except BuddyPress
3. Switch to bp-default theme
4. [Ideally make sure you have updated WP / BP to the latest versions]
5. Then uninstall multisite [which instructions did you follow to do that?]
Does it work correctly if you do this?
If so, the problem is in your theme or your plugins. If not, the problem is more general.
If working after these steps, switch to your theme, then activate plugins one by one, checking functionality at each stage.
If you can report back on that, it should be possible to give more help (if needed!)
[Edit: it would also be helpful if you gave the exact error message you received – with that information, finding the problem may be much simpler]
Thanks for all the answers, Before I start to work on it, let me just explain. I have my site on the .net domain and the .com is pointed to the .net . I am quite happy, (in fact with your help, would like to) transfer the site to the .com (less the multisite) and leave the multisite set up on the .net url. Just take posts ect off once they are moved to the .com
So I am thinking, do I export the database, from the .net over to the .com and make the changes to the files then, to stop multisite. The .com has no database at the moment. Or could I install a fresh wordpress on the .com, install bp and transfer over only the databases of all the buddypress to the .com.
If this is the best way, would I be correct in saying, export the bp files from the .net and import them back up to the .com database. Any pointers on this would be great.
I can have the database in the same host if it makes it easier.
Thanks