Issues when declearing "_objectid_type" to attach a file

[MartinSosa]

Greetings from Argentina!.

Hello to everyone!. I'm having a little bit of troubles to make notes, attachemnts from PowerApps to Dynamics 365. I'm quite newbie in this tech but looking forward to upgrade my skills.

So, the problem I'm having is with the "_objectid_type" to attach a file!, here's my code sample:

Patch(
Notes,
Defaults(Notes),
{
subject: BrowseGallery1.Selected.Name,
notetext: BrowseGallery1.Selected.Name,
_objectid_value: BrowseGallery1.Selected.Instalaciones,
_objectid_type: "abs_instalacioneses", //<-- HERE'S THE PROBLEM!
filename: "img.jpg",
documentbody: If(
StartsWith(
First(Image).fileBody,
"data&colon;image"
),
Replace(
First(Image).fileBody,
1,
Len(
Left(
First(Image).fileBody,
Find(
",",
First(Image).fileBody
)
)
),
""
),
First(Image).fileBody
)
}

)

That's the name of the "EntitySetName" of my custom entity. The issue is this:

"The type of this argument '_objectid_type' does not match the expected type 'Guid'"

So..., I've seen that I've to disable an option on "App Settings" -> "Advanced Settings" -> "Use Guid data types instead of string". 

Well, I don't have that option. So..., I've tried this:

_objectid_type: GUID("abs_instalacioneses")

But I've the next issue: "Ambiguous binding is present. Resolve by sending lookup_type property"

I'm running out of clues, haha.

Any help would be appreciated!.

Thanks in advanced!.

Martin