All the seas and oceans around the world are connected to each other. Water can freely flow between them. That’s the reason tide can occur on them.
On the other hand, lakes are isolated from one to another. Water cannot freely flow between them. That is the reason tide in meaningful amount cannot occur on lakes or any other bodies of water.
When a location on the sea is having high tide, the volume of water increases and this additional volume is delivered from another location that is having low tide. In other words, water flows from locations having low tide to another having high tide.
In lakes, this cannot happen. Even though the Moon exerts the same amount of gravitational force, there’s no way the additional volume of water can be supplied to cause high tide.
Besides lakes, the same thing happens to other bodies of water., including rivers, ponds, pools, etc. Tide can’t occur because water can’t flow freely from or to another location having the opposing tide.
Tides do occur on lakes, but on a much smaller scale. The tides in the Great Lakes is less than 5 cm. Consequently, the Great Lakes are considered non-tidal.
Flat-Earthers often consider the ‘problem’ of the lack of tides in lakes as ‘the failure of modern science to explain the nature’ or something like that. In reality, there is no such problem. Science can sufficiently explain the phenomenon of tide. It is just they don’t understand them.