f stop reading: f00 when using 1.4 extender between EOS R3 and 400mm f/2.8

[rehoopes]

Using Canon R3 with 2.0 extender and 400mm f/2.8 lens, works fine. When switching to 1.4 extender, f stop reading is f00 and nothing works. No camera functions work. This problem did NOT occur previously when using the 1.4 extender. Any thoughts on why this is happening.

[rehoopes]

2x extender works fine. Weight of system is well balanced with no bad stress on the camera/lens connection. Thanks for your input. Will try cleaning the contacts with alcohol as suggested by another.