VS Code 1.51 made the list of suggestions resizable so it’s possible your suggest widget is simply shrunken down to be a single line high.
To fix this, trigger suggestions and then click and drag at the bottom edge of the suggest widget to increase the number of visible suggestions.
Note that you can always use the arrow keys to navigate through suggestions, even if only one suggestion is visible. Use this to check if the widget is simply too small or if there really is only one suggestion