Since 2018, an unexpected number of earthquakes have been occurring offshore Mayotte, in the Mozambique Channel. They are linked to the eruption of the Fani Maoré submarine volcano. Using a recently developed comprehensive automatic catalog, we explore two years of the volcano-tectonic (VT) seismicity between March 2019 and March 2021, and analyse in detail the active structures of the magmatic plumbing system using ~33,000 events. The VT earthquakes highlight three magma storage zones and two aseismic conduits that have never been observed before. The temporal evolution of the seismicity reveals a probable regime change in March 2020. While before, the plumbing system reacted to the drainage of magma from a deep reservoir and to the migration of magma towards the seafloor, it is now responding to new migrations of fluids and to the redistribution of the stress-load across the system's pre-existing faults. This analysis is key to better understanding long-term volcanism worldwide.