JTAG-Problem: Unable to scan device chain on CV GT Development Kit

Dear Community,

1. JTAG no longer works on my CV GT Dev board since yesterday, without any apparent cause. I have worked with an external USB-Blaster cable until now (Error message Fig.1). The cable is not the cause. I tested it with an other board.
   
   
2. I tried to use the internal USB-Blaster, but unfortunately that doesn't work either (Error message Fig.2).
   
   
3. All the switches are to their default settings.
   
   
4. I opened the JTAG Chain Debugger and did a JTAG Chain integrity test for the external USB Blaster (see Fig.3 below). Seems something with the JTAG signal lines goes wrong.
   
   
5. So I had a look at the schematic of the JTAG Header for external USB Blaster (Fig.4) and have looked at it on the board (Fig. 5). I have noticed that some resistors and capacitors are not populated (see red line, Fig.5). But I don't think that's the cause of the problem because it looks like they were missing before when the blaster was still working.
   
   
6. All the JTAG lines from the external JTAG Header and the internal USB-Blaster Port lead to the MAX II on the underside of the board, which configures the JTAG chain and deactivates the internal USB-Blasterwhen the external USB Blaster is connected (Fig.6). So maybe this is the problem. But I don't have an idea how to check this or whether the MAX II can be reprogrammed.

I would appreciate any ideas of what else i could try to get it to work again?

Best regards

Fig.1 Error Extenal Blaster, Fig.2 Error Internal Blaster

Fig. 3: JTAG Chain Integrity Test

Fig.4 JTAG Header for external USB Blaster

Fig.5 JTAG Header on the board

Fig.6 MAX II