Time Machine to NAS ok for 2 days. Failed. Now Finder can't open my NAS but browser can.

Thank you for your reply!

Yes, that shared folder is 100% for the collection of my Mac's TimeMachine backup. There is another separate shared folder for the other Mac here. All the other shared folders open when accessed with appropriate passwords. I can open the TimeMachine backups in Finder using the "name" that the Mac assigned to my laptop and the password I assigned to the shared folder.

1. Note that Time Machine wrote hourly backups for two days right through to the assigned shared folder. I did change both of the shared folder passwords in DSM after their initial setup to make more consistent passwords. See next note.
2. The second Mac here is a family member's M1 MacBook Air on Sonoma. I want to upgrade that older machine to Sequoia but there had never been backup by TimeMachine, so I have been trying to get that backed up before upgrade. I have been trying to figure that laptop's backup problem for a few days. Doesn't *seem* related.

Thank you for replying tonight.

The v7 DSM is up to date, whatever that version number is.

Network topography between Mac and NAS includes WiFi to Synology 2600 that is configured as an access point. That is connected to the WAN router through a no-frills unmanaged switch and that router is connected to my three NAS boxes through another small switch. I have been using this layout with minor variations for about eight years although the Synology router replaced an older TP-Archer access point a few months ago.

MrHoffman, I replied to your question but the Forum software placed that reply "above" under a different person's question.

I see now that this forum doesn't present the conversations in threaded format...

I have run through several different tutorials including Synology's recently updated version (in their Knowledge Base.) I double-checked all the settings. Note that this TimeMachine backup *did* work for a couple of days.

I think it's time to wipe the first one and start over entirely, and I will look at app AutoMounter.

MrHoffman, my ISP's router *does* have WiFi enabled. It's a floor above me. The Synology 2600 access point is 10 or 12 feet across the office from my desk. I'd be amazed if the MacBook Air is grabbing the upstairs channels.My phone shows which WiFi source it wants use as I turn on the WiFi radio. The phone never shows that ISP SSID here in the basement.

Can you help me with these two questions about double-checking credentials in Finder or elsewhere in MacOS networking? Finder's and TimeMachine's [problem]behavior might be caused by a difference in "Group status" in Synology's DSM operating system for NAS operation.

1. It appears I can't go back and re-enter specific credentials to re-connect a network address (shared folder on NAS.) Perhaps I made a typing error setting up a connection. Is this because Keychain is in use? I don't want connectivity functions hidden from me. (This Mac laptop and MacOS is new for this long-time Windows user. I have not researched KeyChain yet.)
2. Can MacOS Finder use different password/usernames when mounting on my laptop several different shared folders on one NAS? Or must all the shared folders to be mounted use the same password? Perhaps DSM requires that they all be at the same level of DSM access permission such as "Administrative". No one tutorial about TimeMachine I have seen/read mentions looking at the credentials, even as the owner of the repository. Once and forever done...