Looking at the log files this is happening when installing the firefox deb so the problem is likely there.
06:31:33 Selecting previously unselected package firefox.
06:31:33 Preparing to unpack .../26-firefox_1%3a1snap1-0ubuntu5_amd64.deb ...
06:31:33 => Installing the firefox snap
06:31:33 ==> Checking connectivity with the snap store
06:32:06 ===> Unable to contact the store, trying every minute for the next 30 minutes
06:47:28 ===> Still unable to contact the store, trying for another 20 minutes
07:02:51 ===> Still unable to contact the store, trying for another 10 minutes
07:16:00 Build timed out (after 60 minutes). Marking the build as failed.
Looking at the log files this is happening when installing the firefox deb so the problem is likely there.
06:31:33 Selecting previously unselected package firefox. firefox_ 1%3a1snap1- 0ubuntu5_ amd64.deb ...
06:31:33 Preparing to unpack .../26-
06:31:33 => Installing the firefox snap
06:31:33 ==> Checking connectivity with the snap store
06:32:06 ===> Unable to contact the store, trying every minute for the next 30 minutes
06:47:28 ===> Still unable to contact the store, trying for another 20 minutes
07:02:51 ===> Still unable to contact the store, trying for another 10 minutes
07:16:00 Build timed out (after 60 minutes). Marking the build as failed.