including/which includes

  1. I am writing a report including a figure and text.
  2. I am writing a report which includes a figure and text.
    I would like to know why #1 is wrong? Why can’t “including” be used here?

It is not specifically wrong grammatically, but presumably the original context indicates that ‘which includes’ should be used.

In simple terms:
which includes = I am writing a report - the report includes…
including = I am writing a report and part of that report will be in the form of…