Answer: This is an unfortunate, but not uncommon, acquisition saga. When companies combine, blending different job classification systems is a tough task. And the new owner usually gets to make the rules.
Your old company apparently paid more, so your salary now exceeds the maximum for your new pay grade. When that happens, raises are typically minimized until everyone’s pay is "in line".
Because no one ever feels overpaid, I’m sure this seems unfair. But it truly is not personal. The “glowing praise” indicates that you are still highly valued. Your compensation just needs to fit the new scheme.
However, your recently doubled responsibilities may provide some recourse. Ask your human resources manager if this new job description might warrant a higher pay grade.