MyTrueAncestry Comparing MyTrueAncestry Results with GEDmatch Results- Why the Difference?

This is my first post and I am not an expert, so please excuse my gaps in knowledge, but I would like some help. I am posting the areas of discrepancy between autosomal DNA results in matches from My True Ancestry and GEDmatch. Please give me your thoughts. It may be due to the setting I used, but if so I would like to run them again. My GEDmatch number is in my profile.
Ancient DNA matches
For GEDmatch, I used the following settings:
[FONT=&quot]Minimum segment threshold size to be included in total = 100 SNPs[/FONT]
[FONT=&quot]Minimum segment cM to be included in total = 3.0 cM
[/FONT]
1. Sigtuna 84005/ NJ2572514
MyTrueAncestry:
14.65 cm Total/ longest chain 12.75 cM, 1586 Total SNPs shared
GEDmatch: [FONT=&quot]No shared DNA segments found

2. [/FONT]Sigtuna kal006/ GT8893268
MyTrueAncestry: 2 SNP chains over 60, Largest chain: 137 SNPsGEDmatch: [FONT=&quot]No shared DNA segments found[/FONT]3. Sigtuna urm160/ PV1449704
MyTrueAncestry: 8.96 cm total, longest chain 3.74, 237 largest snp chainGEDmatch: [FONT=&quot]No shared DNA segments found[/FONT]4. Trans-Volga Forest Steppes kzb008/ TC4794281
MyTrueAncestry: 90.31 cm total, 36.75 cm longest chain, 176 largest snp chainGEDmatch: [FONT=&quot]No shared DNA segments found[/FONT]

5. kzb002_Srubnaya/ FC2917611MyTrueAncestry: 76.79cm total, 16.54 cm longest chain, 1209 total snps, 417 largest chainGEDmatch: [FONT=&quot]No shared DNA segments found
[/FONT]
6. Western Scythian mix DA197/ UM3393611
MyTrueAncestry: 20.75 cm total, 6.26 cm longest; 150 snps total, 9.69 largestGEDmatch: [FONT=&quot]No shared DNA segments found[/FONT]
7. Scythian Moldova scy301/ CG2611850
MyTrueAncestry: 21.18 cm total, 17.07 cm longest, 191 total snpsGEDmatch: [FONT=&quot]No shared DNA segments found
[/FONT]Others do confirm matches, but the numbers aren't equal.
??????

I don't think My True Ancestry is all that accurate, to be honest.