Sponsor document

[Raph123]

Hello, I'm applying for a visa sponsored by an employer. I had the biometrics taken on 6 January 2020 and sent the documents to an outsourced company called VFS Global (only way to apply for a visa in Brazil). The documents I provided are my passport and the invitation letter from my employer.
However, UKVI (UK visas and immigration) sent me an email yesterday saying I need to provide "sponsor document" and I have until 15 january 2020 to send the email with the "sponsor document" attached.
I tried contacting VFS Global, but they just replied with an automated message saying I should contact another company or pay to contact UKVI.
What I am wondering is if VFS Global didn't send the passport together with my invitation letter.
Or if the content of the invitation letter does not contain enough information.
So I am asking if someone could help me out in this, please. Below are the contents of the invitation letter. Thanks in advance. If more information is needed I will provide them.

The invitation letter:
x
The company writes to confirm the invitation extended to [me], technical representative at [company], for technical training at our [city] facility.
[company and description of what the company does]. It is therefore requested by the company that he be granted an entry visa for the visit.
The passport details of [me] are as follows:
x
x
Address in the UK whilst visiting: [address]
Arrival date: [arrival date]
Leave date: [leave date]

[Signature of the Human Resources person]
Signed on behalf of [company]

[CR001]

What visa exactly have you applied for??

[Raph123]

It is a visitor visa with a duration of 6 months. The main reason for the visit is business.

[Raph123]

I just arrived from the VFS Global office (because I could not contact them through email or phone). And according to them, they sent the invitation letter to UKVI.
What I'm currently thinking is that my employer in the U.K. needs to send me a sponsor letter.

[Raph123]

I called the UKVI (UK Visas and Immigration) and the person only told me to search for "sponsor document" on the gov.uk website. The result showed a pdf file that concerns tiers 2, 4 and 5. Which is not my case, mine is a visitor visa.
Also the person could not look up my informations with my reference number.
I fulfilled all the required information on the section of visitor visa with the main reason for the visit being business-related training.
I don't know what other informations are required in this "sponsor document". Could anyone please help me?

[CR001]

Why not simply email the letter you have to ukvi and ask if this is what they are requesting?

[Raph123]

Why not simply email the letter you have to ukvi and ask if this is what they are requesting?

Because the person who asked for it may already have the letter. So I would provide the same document and my visa application may end up getting rejected on january 15 (5 working days after I received the email asking for "sponsor document").
In the same day that I received this automated email I sent a message through the provided email asking what specifically should be in this "sponsor document".
A couple of things that may be mismatching is that in the application form I filled the part "Give details of the main purpose of your visit" as "I will be an intern at [x] company", instead of saying "I will receive training at [x] company". Should this mistake be addressed and corrected in another letter the company writes for me?
Another thing is that my mother instead of the company will pay towards the cost of my visit.
In my occupation I filled with "a student", which is true but may not be related to receiving business-related training in the U.K.
After I receive the training in the company in the U.K., I will work at the brazilian office of the company, should this information be included in the invitation letter?
Also, other than the invitation letter, is it better also providing a sponsorship letter from the company?