1. Rabah and Abaye had neither an Eruv nor a Shituf in their Chatzer and Mavoy.
2. Abaye was unable to use his own food to make an Eruv by having someone else acquire it on behalf of the people of the Chatzer or Mavoy.
3. There is a dispute about whether one can nullify his ownership to someone else, and the other can then nullify it back.
4. There is a dispute about whether a person who nullified his domain to the others and then carried anyway invalidates the Eruv.
5. Rava explains this argument (#4).
A BIT MORE
1. When questioned about this, Abaye explained that it was beneath Rabah's dignity to collect for the Eruv, and Abaye was too busy learning Torah to be involved. The rest of the people living there simply did not care enough to make an Eruv or Shituf.
2. This is because he did not have enough food to spare. According to the Halachah, people may not withhold any of the food of the Eruv or Shituf from anyone involved who wants to eat it, and doing so would invalidate the Eruv or Shituf.
3. If two people did not make an Eruv in their Chatzer, Rav allows one to nullify his possession to the other so that he may carry whatever he wants, and the other may then nullify back to the first person so that the second person can carry whatever he wants. Shmuel says that this second nullification is invalid.
4. Rebbi Meir: He invalidates the Eruv, whether he carried into the Chatzer intentionally or unintentionally. Rebbi Yehudah: He invalidates the Eruv only if he carried into the Chatzer intentionally.
5. Rebbi Meir: We fine a person who carries unintentionally lest one come to do so intentionally. Rebbi Yehudah: We do not administer such a fine.