You did not write an example of how you included your text file.
This example worked for me without problems:
.My table title
[cols="1,1",options="header",]
|====
2+| Headline, spanned above two columns
|include works, no need to mask the pipe a| include::test-include.adoc[]
|works not, include command not recognized | include::test-include.adoc[]
|====
Surely this works anyway
include::test-include.adoc[]
test-include.adoc consists of:
[oc:bind] | Bind result: