The short answer
After years of supporting board syncing at scale, nearly every “boards stopped syncing” report traces to one of five causes, in this order: (1) column names/types don’t match exactly, (2) a status column can’t accept a new label, (3) permissions on a private board, (4) rate limits during bulk operations, (5) a webhook got removed. Work the list top to bottom — each has a fast check.1. Column names must match — exactly, including case
Columns sync when the name and type match on both boards. “Due Date” and “Due date” are different columns; a Status column won’t sync into a Text column. The fastest check is column mapping — it shows exactly which columns will sync and creates missing ones in one click. Full walkthroughs: columns aren’t syncing · column mismatches.2. The status column won’t accept a new label
The classic silent blocker: the destination board’s status column is at its label limit or restricted, so the incoming value can’t be written — and the failure cascades into what looks like “one-way sync” or “boards won’t connect.” Check whether the destination status column can accept the source’s labels (add one manually as a test).3. Permissions and private boards
Automations act as the user who authorized them. If that user can’t access the destination board (private board, revoked access, changed role), item creation fails — sometimes loudly (“no permission to duplicate pulses”), sometimes quietly. Verify the authorizing user is a member of every destination board.4. Bulk syncing and rate limits
Sharing hundreds of existing items at once runs into monday.com API rate limits. Use batch actions in moderate batches (10–15 items) rather than one huge push, and let a batch finish before the next. For very large boards (thousands of items), stagger by group or status.5. Webhooks were removed
Syncing rides on board webhooks. If an admin cleans up webhooks or a board is duplicated from a template, sync events stop arriving. See why SIMB adds webhooks and how to restore them.A board is missing from the destination board list
This is a different symptom from “boards stopped syncing” above — it shows up when you’re trying to set up a new share or automation and the board you want isn’t in the destination list at all, or you can’t add the automation because of it. Check board type before anything else:- Board type must match. SIMB connects regular boards to regular boards, or multi-level boards to multi-level boards — it does not currently support connecting a multi-level board to a regular board (or vice versa). The destination-board list is filtered to only show boards of the same type as the board you’re working from, so a board of the other type simply won’t appear, no matter how you search.
- Only once both boards are confirmed to be the same type, if the destination still isn’t listed and it’s a regular board, apply the older fix: add a subitem once on that board so monday creates its subitem structure, then try again. This only applies between two regular boards — multi-level boards always have a nested item structure and don’t need this step.
- A working older connection to that same board doesn’t rule this out. Shares and automations created before this restriction keep running even though you can no longer create an identical new one — a cross-type automation set up months ago can still be firing successfully today while a new attempt to the same board is missing from the list.