I can't add a new user

I can’t add a new user
I click on the user’s button. A blank page was loaded. I have repeatedly installed it several times, but it still can’t be solved!

Wouldn’t it be nice if you provide some information about your hardware and software environment first before you ask a question, instead of providing nothing than a question? How should someone give you an answer without any valuable information?
Have you already used the search function of this forum to find an answer on your question?
Have you checked the Nextcloud and system log file in advance?
etc., etc., …

Thank you for your reply
CentOS 7.6.1810
PHP 7.2
Mysql 5.6.47


I did not retrieve the error in the log system.
Thank you very much. At the same time, I’m sorry for the trouble.

You haven’t answered all question and didn’t explain what else you have done to narrow down the problem. What about this

https://help.nextcloud.com/search?q=blank%20page%20add%20user

Thank you for your reply again. I come from China, and there may be some language problems in the process of using the community, so I can’t find the answer. I’ve looked at the link you sent me, but I didn’t find the relevant directory in my server: / var / www / nextcloud