thank you for reporting this.
We have checked this and it seems there are two different issues:
Everything seems to be ok with the tile T15TTF but we got a response 500 for an opensearch call, which is made in a background. This needs to be fixed in sentinelhub-py package and we added it to our backlog.
Tile T14TQM is indeed missing in an index thus it can not be found even though the data is available at AWS.
One option to download the data anyway for these two tiles would be to download the whole products: sentinelhub.aws --product S2B_MSIL1C_20181106T171509_N0207_R112_T15TTF_20181106T203828