Which one is correct?

There is no analogue of such a service.

There is no analogue of such service.
"analogue" is actually the British English spelling. "analog" is American English.

"unique" already means there is no other such service, so you don't actually need to say anything else. I suppose it doesn't hurt though -- especially since "unique" has been so weakened by overuse. I don't think "analogue" is quite the right word. You could say:

"The company provides a unique IT service; there is nothing else like it (nowadays)."

"provides" (or "offers") seems better than "renders".

"nowadays" suggests that there may in the past have been similar services. If you don't mean that then I would delete it.
Both are theoretically possible I suppose, but neither seems very likely and I suspect this may not be the natural way of saying what you mean. I think more context is needed.
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Something like this:

... The company renders a unique IT service. There is no analogue of such (a) service nowadays. ...
Shurman, I don't understand what you mean by "analogue" here.

Can you say it another way?

There is no longer an analog version of this digital service?
I have just found that 'analogue' is an american variant of 'analog'. I want to say that none of other companies renders a similar (the same) service. Only the mentioned one does.
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 Mr Wordy's reply was promoted to an answer.