User name problem with space

This is the first time I’ve used the Membership Request Web Part. I use Sharepoint 2016. Users successfully create accounts. There is a problem with usernames that contain a space (e.g. user name is Chris Coulson). Users cannot log in again because they receive an incorrect username error.
Is there a way to change an existing username?
How to prevent the creation of accounts with spaces?
Any advice is welcome.
Best regards

I am able to login to SharePoint 2016 with a username with a space in it. I can also create and manage users with a space in the username. I wasn’t able to replicate any issues with having a username with a space in it.

There is no built in way with the FBA Pack to change the existing username, as the username is used to correspond to a sharepoint user profile. Potentially you could change the username in the database, though you’d also have to migrate the SharePoint user to the new username. If it’s a new user it’s probably easiest just to delete the user and recreate with the desired username.

Thanks for the reply.

You’re right. I was able to create a new account with a space in the username. Everything works.
Obviously, I’ll have to take a closer look at the problems users have when signing up. There were several users with the problem and they all had space in the username. I thought it was a problem, but …

Thanks anyway.