Inactivity timeout acts differently on mobile vs desktop and web. On mobile, this is non configurable. However, on web and desktop, this can be turned on and off and a inactivity duration can be configured.
On the mobile app:
After 30 minutes of inactivity, you'll be prompted to re-authenticate with your PIN or biometrics before continuing.
This is mandatory for all mobile devices and can not be further configured or switched off.
This includes tablets.
On web and the desktop app:
To turn on Inactivity timeout, go to Settings > Security > Inactivity timeout
Use the toggle to turn the feature on or off. Update the number of minutes to change the inactivity duration (before sign out).
When enabled, inactivity timeouts will require a full re-authentication (including MFA, if MFA is enabled).
Unable to update your Inactivity timeout settings?
Org admins can set an org-wide default that overrides and greys out the per-user setting. If this is the case for your organisation, you will not be able to make any changes for inactivity timeouts.
Org admins can set this in Organisation settings > Security & compliance > Inactivity timeout
Timing out unexpectedly?
Your inactivity timeout settings are for web and desktop only. For mobile devices, including tablets, a default 30 minute setting is applied and this cannot be disabled.