There was no point advertising because there was no competition, all the companies were nationalized and no matter how well or badly they did - their employees earned the same. If you persuaded people to buy your washing powder instead of the other available washing powder - that just means the queues for your washing powder will be longer.
There was A LOT of communist and anti western propaganda tho. But no advertising is perfectly possible.
For example, for banks appear problem, people avoid to pay credits, so need some enforcement - powers approved confiscation of property to pay credit, but with exceptions of unprotected people, so bank cannot confiscate from pensioners, when child registered in property, and few others, so literally huge percent of citizens now protected from banks, and this new law is step back, not progress.