Question about Synology DS923+

Hello, I'm sorry to bother you with the following problem, but your help will be appreciated. On 13 April 2020, I placed an order with you and you delivered the following product: 1 x Synology DS718+ (2 x 8Tb, WD Red, 2GB) CHF 1'054.00 I have been using it as a TimeMachine backup for my various Macs without any problems. When I switched to a new Mac, access to the disk was corrupted and I have not been able to use it since. I'm asked for a password but it's no longer recognised. What do you suggest? I also plan to order a DS923+ with 4 x 10TB from you quickly. Your help will be greatly appreciated. Best regards, Eric T. Rauch