Registering / login issues

[Housti]

Hello

A lot of our students 200/1000 have issues registering or signing in into their account. They clicked on the link to register, which were sent to their mailaddress when I added them as a user in our library.
We got some "Too many requests" issues from our WAN while registrering all of our students, just for your information.

The errors are always the same:

Registering:

Above the form:
The user could not be saved. Please try again. (translated from Dutch)
At E-mail:
E-mail is already taken. Please try another.

Signing in:
Last action: Invalid username or password. Try again.

All the students use their school mailaddress. This is @lyceumgenk.be.
Can you please look into the cause of this issue and come with a solution?
Thanks in advance.

Stijn Houben
IT admin
Lyceum Genk
Belgium