Whether the German forces planned on using the Maginot Line, I cannot attest to, that’s for someone else to answer. Apart from that, the question arises whether years of mobile warfare could or should be forgotten in favor of stationary defensive positions.

I can, however, give some insight from a logistical and structural perspective as to why the Maginot Line was not easily usable for German forces. The layout of the Maginot bunker and fortification systems was strictly designed as an anti-German construction.

What do I mean by that and what’s the importance regarding your question? The same way medieval castle walls are designed to be used against an enemy on the outside, the Maginot line is pointed outwards of France and would have serious problems were it to be used in the opposite direction.

First off, and maybe the most observable point, the bunkers that house artillery and other weapons, are turned towards the direction from which a German ambush would be expected. The holes for the guns, the doors, etc. are all on the wrong side to defend from an enemy that approaches from the French side.

The less obvious part of the equation, since it’s deep underground and thus not immediately visible, is the support structure. In a broad network of underground tunnels and bunkers, everything from sleeping quarters to munition storage and cafeterias is also on the wrong side. That deals defenders two impossible tasks. One, keep an attacking force outside of the tunnel entrances that are extremely exposed since they are not too fortified and away from the actual battle fortifications. Most often, the main artillery cannot defend the entrances that are behind them, for example because there‘s a ridge or mountainside between them or they simply cannot be turned that way. Two, get supplies into the tunnels while the enemy is attacking. Worst case, the defenders supply would have to be moved across the fortified line that’s above ground, over a mountain/hill spiked with anti-Tank or anti-vehicle infrastructure, towards the enemy, where the access points are.

You can search for illustrations of the Maginot Line that show the expansive underground support system. You’ll see how the entire structure is exposed from the back and most likely impossible to defend because of it. Occasionally there is a bunker on the backside, but that is not enough to withstand an attack.