The Venezuelan military has not budged  from its support for Maduro:
Underpaid, underfed and humiliated by the autocratic turn their once-rich and democratic country had taken, the armed forces were the linchpin of the U.S. administration’s strategy. Some U.S. officials predicted that Venezuela’s military would flip en masse within days.
Nearly three months later, Venezuela’s top-heavy military remains largely intact under President Nicolás Maduro. The once-brisk pace of defections to neighboring Colombia has slowed to a trickle. Fewer than 1,500 Venezuelan soldiers, relieved by the Colombian government of their weapons and uniforms and housed in sparsely furnished hotel rooms near the border, now sit waiting for something to happen.
Regime changers always assume that it will be easier, faster, and cheaper to topple a foreign government and deal with the aftermath than it really is. Almost three months since the U.S. and other governments threw their support behind Guaido, their absurdly optimistic assumptions have been proven completely wrong. At some point, the administration and opposition will have to acknowledge that their attempt at regime change has failed, but they continue to cling to their fantasy that they sanction Maduro into submission. The sooner that the administration accepts that its policy won’t work, the sooner it can lift sanctions and back off from its misguided demands.
The military’s refusal to switch sides should have been taken as a given. The fact that the administration and opposition assumed that they would rapidly abandon Maduro shows how little thought they gave to the consequences of what they were doing. The top brass has no incentive to abandon a system that benefits them personally, and the officers underneath them have ample reason not to take major risks by siding with the opposition. Add to that the presence of Cuban intelligence officers who are there to learn about and squash any possible uprising, and you have a recipe for stalemate.
The article goes on to say this:
While they are hesitant to criticize, some U.S. officials express exasperation with the Guaidó-led opposition, which they see as failing to win the support of the Venezuelan armed forces even as they demand U.S. intervention.
“The opposition hasn’t gained their confidence,” the former senior U.S. official said, and “has done a lousy job at assuaging their fears.”
It is fair to fault the opposition for wishful thinking, but it is the administration’s failure to take the assurances of the opposition at face value. When Guaido reportedly told  Pence that half the military would quickly switch sides, the appropriate response was to assume that he was telling our government whatever they wanted to hear instead of telling them the truth. Unfortunately, the administration is full of ideologues and fools that want to believe anything that gives them a shot at bringing down a government the don’t like. The Trump administration thought they had a quick and easy foreign policy victory lined up for them, and months later they are discovering that they didn’t have the first clue what they are doing.