Importing wallets is disabled when blocks are pruned (code -4)

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Hey

I tried to upgrade my wallet from Blockmarket 1.??.
My old laptop died but i still have a backup of the directory:
/Users/USERNAME/Library/Application Support/Syscoin
which includes the wallet.dat file.
I followed this guide:

Blockmarket or Syscoin 2/3.x.x to Syscoin 4.x.x --- Upgrade Guide

Important Preliminaries - Do not skip this section at any rate! Please read them carefully, we mean it. If you have already upgraded to Syscoin 4.0.0 successfully, you only need to install the latest version of Syscoin 4.2.2 and skip this guide. If you have not already done so make a backup of your wallet.dat. You can find it in The Syscoin data directory. This procedure will ‘dump’ your existing Syscoin 2/3 wallet via Blockmarket or Syscoin-Qt 2/3 into your public folder, and ‘import’ this w…

To do the dumpwallet i had to install Blockmarket 1.2.3 where i simply changed the Syscoin folder with my backup folder. After that i could see my coins in the wallet.
After that I installed Syscoin 4.3.0.
But the last step of the guide is not working for me. When i try to Import my sys3dump.bmwalletdump file, the console gives me the error:
“Importing wallets is disabled when blocks are pruned (code -4)”.
I tried the import on an other PC with a new Syscoin 4.3.0 installation. Same result.

Is there a Problem with my dumped wallet?
Or does an other way exist to get my privatkey out of my wallet.dat file?

Thanks for your help.