Niantic Labs has been killing 3rd party apps whenever they got a chance to do so. It has been previously reported that the developers had some tweaks on the game's security system which blocks several hacking apps. However, it was later discovered that Niantic has dealt so much damage to these 3rd party apps than most of the players thought. The most popular app, FastPokeMap, has been currently experiencing several deadweight.
According to Otakukart, there have been several tweets posted from various apps including the FastPokeMap notifying their users that the apps are not functioning because they will have to reverse the api once again. In addition, yesterday, it was reported here that Niantic has added a warning message feature on the game to warn their players to stop using these 3rd party apps. It was also explained that it will cause a permanent ban whenever a user still insist on using these unauthorized apps.
Several recent evidences show that this warning message is effective enough and some players are slowly heeding to the said notice. Based on the reports, whenever this 3rd party apps are functioning, it brings traffic to the server and it is like DDoSing the server which is considered illegal. That is why Niantic has been trying their efforts on getting rid of these apps from functioning in order to bring back Pokemon Go's stability.
Niantic is still encouraging players to change their culture of gaming and stop using these 3rd party apps. It is also reported that the company will be bringing several feature additions in the future which do not require you to use these unauthorized apps. This move from Niantic is only a first step towards making the gaming community free from players who tried to ruin the game's mechanics. In addition, using third party apps is against the rules and as we all know that playing against the rules results to a ban.