What you are not showing is how you save a value to
item.UserProperties("request"). From your description of the pages
that are seen, I infer that there is no value in
item.UserProperties("request") and the code is falling into the else
clause.
request is the value of the dropdown assigned for the
combobox (name - combobox1). On the properties page for Combobox1, on
the value tab, I have assigned a new field named "request"
(Property to use As Value)

Where is the form published?
The Form is published on a public folder

Does the recipient have access to it?
The recipients have access to this folder.

Also, when I send a reply mail from the recipient, the form does not
get displayed. The form gets displayed only if I forward it again from
the recipient to another user.