@Szina - As per the the following Help Center article, the absolute maximum connections to a board at one time is 1,000 (editors or viewers) and Miro states that they can't guarantee performance if you go over 300 editors on the board at one time:

https://help.miro.com/hc/en-us/articles/360013912300-How-Many-Users-Can-Collaborate-on-a-Board-Simultaneously

All 9 of your team should be able to edit at the same time. Keep in mind, there will be other factors to consider, e.g., internet connection speed, computer/device performance.

When you say only 4 or 5 could "see the board", do you mean they could see and edit and the others couldn't see/load the board at all or do you mean the 4 or 5 could only access the board as "viewers", i.e., they could not edit it?

Hi @Robert Johnson, 
Thank you for your fast answer.
 

No they were not able to see the board.

I should add the info, that the board was integrated into a monday-board. Miro is an integrated App in monday, and i wanted to share the miro Board with my team members in monday. Is monday the problem?

And do my colleagues need to be signed in as “team members” of my account?

Thank you and best wishes,

Szina

@Szina - It sounds like you set the board's Share settings to "Anyone with the link Can view" in order for it to be viewable when embedded using the monday.com integration, which is fine, but only signed in team members can edit a Free Plan board, so your team members will need to sign in to the board when viewing it through monday.com.

They may be able to fully open/"pop it out" of monday.com which should open it in their default browser, in which they are most likely already signed in to Miro from.