Hi, Welcome to the Forum.
Sorry but no good news I don't think. Unfortunately Envisioneer 6 will open TFP 14 files because it is a later version but in effect you are going backwards, so there is obviously something in the later version (Env 6) that has been changed and is not in TFP yet. You would probably find the TFP V15 will open it (unless you have added in something that does not get included in TFP 15) but of course TFP 15 is not available yet and presumably you cant afford to wait and see if it will open it.
Something you could try: In Settings / Program Settings / General you will see the' Startup Project Template'. Find the Envisioneer one (click the ... link button to see where it is) and try opening TFP using the Envisioneer template instead (Select the Env template from within TFP - be sure you know where the origianl TFP is to change it back). This has been know to activate some Env functions but can also cause some unstability too. If it works it may get you over this hurdle but it may sill not work, as you are still trying to open a later version with a program using older functionality.
The only other option would have been to Export it as a DXF but all exports are disabled in the trial version of Env6. Even then the DXF would not have been editable, except for textures. Even the size may have been an issue too as the DXF exports are quite big. This may still be your only alternative but would mean asking someone on the Envisioneer forum, who has the full version, to export it as a 3D DXF for you. I got caught the same way myself, created a piece of furniture in Env6 trial just as a test, then decided I wanted to add it to my TFP catalogue. Someone exported it as a 3DS for me (
http://www.cadsoft1.com/customercare/viewtopic.php?t=6166).
As a 3D DXF, inported into TFP, you should still be able to create plans, elevations etc and add text, dimensions and comments but would not be able to change anything in the model itself. You could possibly add to it though, on another location. If you are wanting to do plans you may find the PDF in this post useful (
http://forums.turbofloorplan.com/index.php/topic,877.0.html ) if you have not see it already. If you are only interested in the 3D images, then it could be a challenge reassigning textures. The DXF file can however be opening in TurboCAD and you would be able to edit it there. The version of TurboCAD should not matter as DXF is a standard independent format. Textures would have to be reassigned if you are interested in 3D images but producing plans would be no probelm in TurboCAD.
As a last resort, get someone on the Env forum to export it for you as a 2D DXF and use it to trace a new model in TFP.
Sorry I can't offer some other solution.
Allan