After the sudden and unscheduled visit of Iran’s foreign minister Mr. Zarif to Ankara, this address change was announced by Iran.
This sudden change of address was interpreted as the Iranian state’s escape from Azerbaijani Turks and withdrawal from Tabriz.

Reasons are as follows;

The Iranian state experiencing the legitimacy and authority crisis in the ethnic regions of South Azerbaijan. In recent years there has been a considerable intellectual and emotional break between the Turkish population and Tehran dominance, an important determinant in Iran.
Iranian government making this summit in Tabriz would represent the city to the whole world. But the situation turned out other way, and played against the doer.
News of Prime Minister Recep Tayyip Erdogan caused special sensitivity and activity among South Azerbaijani people. Mr. Erdogan has became a symbol of Turkish national ascension in the eyes of the South Azerbaijani Turks as well as many others. Mr Erdogan’s ruling period in Turkey with Turkish national consciousness experienced a significant rise. It is also a fact that Mr. Erdogan is a friend of Azerbaijan.
For this reason, a campaign was launched in the southern Azerbaijani social media to welcome Mr. Erdogan in Tabriz, and this campaign grew rapidly. South Azerbaijan Turks in Tabriz started to prepare to meet Mr. Erdogan with national slogans.
This has seriously disturbed Tehran’s sovereignty. It experienced the problem of legitimacy and authority in South Azerbaijan, if they met the president with a big crowd in front of the eyes of the worlds media it would have been a complete fiasco and disgrace for the Iranian government. This situation has caused a serious panic in Iranian state.
For this reason, the minister of foreign affairs came to Ankara and went directly to the headquarters of the AK Party, contrary to official conventions, and later announced that summit would be held in Tehran, not in Tabriz.
This movement of Tehran was interpreted as the escape and withdrawal from Tabriz and the history has noted in this way. This incident attracted the attention of Turkey and the US as well as Russia, Israel and Europe.