Problem:
the pools size is too small for the amount of data and/or retention period
Common Solution:
Increase pool size and then reduce retention period if you "must" keep pool sizes to a specific amount of space. Generally "unlimited" pool sizes are recommended. Restart service on FD and SD (Linux: service bacula-fd restart or on Windows: restart the service), then restart job and monitor.
Problem2:
You have removed volumes manually from the SD instead of purging/removing via GUI
Common Solution2:
please navigate to Storage Pools within your GUI, edit volumes, and delete all volumes you had previously removed directly on the SD