Is your HD621 running the latest fw version (1.1.1)?

Have you also tried typing (resetting) the HD621 using Mconfig?

I presume the RS232-USB adapter works fine with your G68?

I think with the HD621 you can also store a new config, without fetching first.

#1 568.2mm, HD621, G91DH, 513, 511, DSP3100 , DSP33C , DSP33, 2x MJ Pro 50 MKI, M1500
#2 G68J, HD621, DSP3100, DSP5200HC, DSP33, 3x MJ Pro 50 MKII, MS200, SB Touch, Vertex 2
#3 G61rsl, HD621, 596P, DSP7000, DSP5500HC, DSP33, 2x MJ Pro 50 MKII, M1500

Applied mods: NOS-SRx Filter by Mr. Apodizer
Mr. Apodizer Digi box