This is normal - dividends do not land in your account instantly. For SPY they seem to take about 6 weeks to come through.
Essentially, a company sets an 'ex-div date', the day before which anyone holding a position in SPY will be recorded to receive the dividend.
If you hold SPY on or after the ex-div date you don't get the dividend.
The 'Pay Date', set by the company, will be known to you at the time -- this is when you will actually receive the money (i.e. about 6 weeks later)
For instance, SPY's last quarter dividend of $1.1349 (ex-div date: 19th Dec 2014) had a pay date of 30th Jan 2015.