Hi @Matio,
In the code that you posted in the previous reply for HAL_ETH_MspInit it seems like the STM32 generated code is not enabling the ethernet interupts, the code should look something like this at the end of the HAL_ETH_MspInit() definition (ignore if you have enabled it by manually adding those lines elsewhere):
/* ETH interrupt Init */
HAL_NVIC_SetPriority(ETH_IRQn, 5, 0);
HAL_NVIC_EnableIRQ(ETH_IRQn);
HAL_NVIC_SetPriority(ETH_WKUP_IRQn, 5, 0);
HAL_NVIC_EnableIRQ(ETH_WKUP_IRQn);
You could enable those settings in this part of the CubeMX (not enabled in the below image):
