Thyatira was the smallest of the seven cities on an ancient Roman mail route. Beginning in Ephesus one would travel north to Smyrna and then to Pergamum. At this point the mail rider changed to a southerly direction and came to Thyatira on the left of the road from Pergamum to Sardis. The church of Thyatira is sometimes called the corrupt church, but I believe this has more to do with a forced historical interpretation of the seven churches than anything else. The idea that these churches represent seven eras of church history is completely false. It is eisegesis rather than exegesis. Jesus had some very good things to say about this church, and to conclude that it was a corrupt church in order to fit it into a corrupt era in church history is simply ridiculous. There is absolutely no good reason to do so. In fact, it is slanderous to do so, in my opinion, and that against brethren whom Jesus commended for their labor.
Jesus said he knew all about the church’s works (G2041) at Thyatira. He said that he knew about their love and service, and their faith and patience. He also said their works of late were more or greater (G4119) than what they had been at the beginning (Revelation 2:19). This was a commendation Jesus gave to no other church on the mail route.
The business or work (G2041) of the church at Thyatira was the same as that of each of the other six churches. In other words, the business or works (G2041) of the seven churches (Revelation 2:2, 9, 13, 19; 3:1, 8, 15) had to do with preaching the Gospel. This Greek word (G2041) had to do with both evil and good works of men (Matthew 5:16; 23:2-3, 5), but it was particularly used for the work of spreading the Gospel (Acts 5:38; 13:2, 41; 14:26). It seems the believers in Thyatira carried out the business of preaching the Gospel as a labor of love. They truly labored to serve others with the word of God, and they trusted in him for the success of the things they did, rather than trusting in their own strength. Therefore, they waited for the word to produce its fruit and endured the contempt of the enemy, while doing so.
Apparently, the church at Thyatira grew more confident and stronger, as they continued to preach the Gospel, for the Lord said their works at the time of his message to them exceeded their works in the beginning. Whether this meant their works were more abundant or greater in quality isn’t said, but the Greek word (G4119) could mean either. Nevertheless, judging from what the Lord had against the church in verse-20, it probably means their works were more abundant, because, permitting unbelievers to influence one’s work in the Gospel, seems to indicate the quality or excellence of making disciples of new believers had not continued to improve from the time of their beginning.
It appears that some disciples were being influenced from outside the believing body, and because that outside influence wasn’t challenged, new believers were being lost or won over by the enemy. Notice that Jesus said the messenger or leader of the church at Thyatira (Revelation 2:18) tolerated Jezebel (the unrepentant Jewish state) to teach error and lead his disciples away from the truth (Revelation 2:20). That is, false teachers (from the Jerusalem authorities) seem to have been permitted at least an element of free reign to teach without being rebuked or challenged by church leaders. This caused some believers to embrace error as truth, and the process is implied in the picture of ‘eating things sacrificed to idols.’
Thyatira doesn’t seem to have left its first love of the Gospel, as the church of Ephesus had (Revelation 2:4). However, on the other hand, neither do they appear to have “tried them which say they are apostles, and are not, and hast found them liars” (Revelation 2:2). It seems they love the Gospel and love their service to Jesus in preaching it, but they were too willing to accept the persons of folks claiming to be believers who actually weren’t believers at all.
 Strabo: Geography; 13.4.4.