[sudhanshu]

First problem php.log file not creating but my email.log is created. Path is set and directory is writable.

Second issue:
When user try to reset password he gets email but gets the "Invalid server response" as alert.

How to fix this ? Any help or steps are appreciated.

Using vBulletin 5.6.2

[yilmaz]

An installed product might be preventing this process.
Disable Hook System
site-address.ext/admincp/options.php?do=options&dogroup=plugin

Try to reset the password again.
If it is successful, you should disable it one by one and try to find out which product.