I learnt this the hard way .  I recently  re installed on my blogs. I had 5000 registered users in that blog.  I did a back up of my users from the blue host  cpanel.

WordPress plugins for  import users does not work

Then i re installed the blog  and tried one  wordpress back up plugin after the other and they all failed to import my  CSV back up file of the 5000 users. I typed import users and tried the first five plugins that import users with csv files . There was one that at least did something and worked , but worked wrong ( CSV user import – Visit plugin site). It uploaded the file but put the passwords salts as the username.

It got all messed up,  then i realised in should have done this in the first instance. I went back to my bluehost cpanel / php admin  where i did the back up in the first place , and then deleted all the wrong entries  that got uploaded ( deleted 400 entiries in one go  and repeated—maybe you can do more than 400 )

Then i  clicked import and imported the csv file an hey presto in a second all the 5000 users were back up.

This goes to prove that use the same tool or process to export and the same tool to import , wether it is from the php my admin  or then from the wordpress admin panel , make sure the plugin does import and export or then  the same author of the toll has created similar plugins for import or export ,w hereby you have a better chance of them working both ways together.

Also attached some snapshots of the cpanel and php my admin in blue host.

Let me know if this helped you and give us a like