I set the Email method as "PHP" in Global Settings, and I only received 1 Response submission mail while I had submitted at least 5 response. Then I changed the Email method as "SMTP" and fill all the blanks, but this time it didn't work at all.

How can I find out what is wrong? I can't find a log.
And I also suggest to add a test email issues in the Email Settings Page.

ps: my LimeSurvey version is 3.17.8-190722, sugarhosts virtual host with php 7.2

I cannot speak to your SMTP settings but if PHP mail worked once it should work for all subsequent submissions assuming the address is correct ant the mails were not caught by spam filters.

The notification email uses the same email address.
I had checked my email server, there was not any mail filted as spam.

Any way, Thank you for your reply.