Ok, here's the answer provided by the Colonial Marines Technical Manual:
For context, the final chapter is written entirely from the point of view of Weyland Yutani / Company employees who are working on gathering all available intel on the Xenomorph, having learned of its existence from the Sulaco's flight recorder during the opening of Alien 3, Ripley's scan in the EEV, and all the data they obtained from recovering Bishop from Fury 161 (they did not know / believe in its existence prior).
So, first, the colony transmitter;
It went down three weeks from Burke sending instructions to the colony to check out the co-ordinates. To quote the movie;
"Hey Al, you remember those wildcatters you send out to the middle of nowhere LAST WEEK past the Ilyum range?"
"Yeah, what?"
"Well one of them is on the horn, a mom and pops survey team, wants to know if their claim will be honored?"
"Why wouldn't his claim be honoured?"
"Well because you sent them out there on company orders maybe, I dunno!"
"Christ, some honch in a cushy office back on Earth says go look at a grid reference, they don't say why, and I don't ask.. I don't ask because it takes TWO WEEKS to get an answer out here, and the answer is always don't ask."
So two weeks for the company to receive Burke transmission from Earth, one week of searching; there is your three weeks. The transmitter was down. There was no communication.
That quote from the CMTM is also when Weyland Yutani first learn what Burke has done. You know.. since he was working alone with his own interests in mind.
Why didn't WeYu believe in the alien prior? Two reasons, first;
They thought Ripley was a nut job, and second;
The company never knew about the Xenomorph. Special order 937 was initiated by another greedy slime ball like Burke who were operating with their own interests at heart and quickly covered their tracks when the Nostromo went missing. This was the first WeYu learned of that also after digging through files.
So to finally put this to bed, no, there was no communication from the colony at all as the transmitter was down for whatever reason, and there definitely wasn't any conspiracy at play. Weyland Yutani get conclusive evidence of the Xenomorph from the sulacos flight recorder through the network and immediately mobilise a task force - this is the first time it's actually 'The Company' perusing the xeno and not just greedy employees working alone hoping to score a payout from the Bio Weapons Division.