It is likely you overwrote the Admin password and the salt is different.
Request password reset for your admin account. If that doesn’t work, go into the data base and ensure the email account for admin is set to your email address (phpmyadmin is a good tool for this)
Once that is done, re-try the password reset.
The problem is that the attachments folder needs to be writable by the web-server.
Changing the folder permissions to 0775 does not help if the Group ownership is not in the group for the web server.
You may need to run both of the following commands
chown -R <user>:apache <wp install folder>/wp-content/plugins/si-contact-form/attachments
chmod -R 775 <wp install folder>/wp-content/plugins/si-contact-form/attachments
This assumes that your webserver is running as Apache.
