Rsync suddenly stopped all backups from another NAS

My Cloud OS 3 Personal & Network Attached Storage My Cloud EX4
1

Hello
4 days ago I backed up a folder from Synology NAS to my Ex4100 WD it worked fine I left for the weekend and returned and suddenly the Synology job isn’t activating it says my WD is online but I get an error every time I activate the job,

2020-12-07_123444
2020-12-07_123444987×332 11.9 KB
this is my WD configuration with port forwarding
and this the error get on my Synology
2020-12-07_123543
2020-12-07_123543967×427 26.8 KB
I mean it was working fine for 2 days after the weekend it stopped working, my firewall is off the ports are open, I tried restarting both NAS.
??