Even if it looks clean, it could be gummed up inside the segment. I have had Coronas where someone must have sprayed oil in the segment which congealed to where all the keys were frozen. It took multiple cleanings to free it up. It can look clean and still act like it is glued solid.  Do not manually raise the typebars without depressing the corresponding key; on these Coronas, the typebars won't move without the corresponding key being depressed at the same time. If you try to pull the typebars with your fingers without pressing the key, you could pop the link, which would be fixable, but should be avoided. Never force a key. I would try to free up one key first, to test whether it is an overall segment cleaning issue. If cleaning frees up a key, then you know to continue with the rest. If you cannot free any keys, and they are completely jammed to where they don't even move part way, then it might be an issue with the universal bar being impeded, or something that would effect all the keys from the start point. I don't think it is the line lock, as I believe the keys would still move part way if it was stuck.