First, please post complete code so we can compile the sketch. The #include <FlexCAN_T4.h> is missing.
The sender is working fine.
The receiver needs a can1.events()
Change your code to this:
void loop() {
can1.events();
if...
With the FlexCAN_T4.h library you can call the error(CAN_error_t &error, bool printDetails) function.
This will give you these type of errors:
typedef struct CAN_error_t {
char state[30] = "Idle";
bool BIT1_ERR = 0;
bool BIT0_ERR = 0...