But their eyes were holden that they should not know him.
Note 4 at Lu 24:16: It is amazing that these two disciples, who were well-acquainted with what Jesus looked like and were talking about Him at that very moment, didn't recognize Him. This same thing apparently happened to Peter and John with some other disciples at the Sea of Tiberias (Joh 21:1-7 and 12).
In this instance, Mr 16:12 says that Jesus "appeared in another form" unto them. This was not another form in the sense that Jesus' physical appearance had changed. Jesus still had the nail prints in His feet and hands and the spear wound in His side (Joh 20:27). Therefore, His physical features hadn't changed, but He now had a spiritual body (1Co 15:44) that could only be spiritually discerned (1Co 2:14). Jesus' spiritual body was visible to their physical eyes but only recognizable to their spiritual eyes.
Lu 24:15 reveals that they were not operating from their spirits but were reasoning in their minds (Ro 8:6). This was what blinded their eyes that they should not know Him.
Likewise, Jesus is always with us (Heb 13:5), but we often fail to recognize His presence with us, because we are blinded by our carnal minds (Eph 4:18).