What the fuck are you talking about? For once until the end of the Cold War it was ILLEGAL UNDER THE CUBAN LAW to invest in the first place, you know "profit is theft" and all that jazz, so it was illegal.
When the Soviet tit ran out and Cuba found that its system only works when you get free oil from the USSR and resell it to other countries at real market rates their country when to shit so they changed their law to get a lot of investment.
In the 90s tons of investment came and what happened? Cuban government stole it, like they did before, tons of debt went unpaid and countries cut their losses, there is still business being done with Cuba but there is no credit, since there is nobody stupid enough (with the exception of Mexico right now) that gives credit to Cuba.
And since the country produces NOTHING of worth there is no way to get hard cash to pay for stuff.
This is 100% the fault of socialism, go figure, people don't want to work for free, because funnily enough when communists said "under communism everything will be free" the only thing that became free is labor, things still cost money but you have to work for fake money.